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Market  Gardening.  By  F.  L.  Yeaw,  Manager, 
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Exercises  in  Farm  Dairying.  By  Professor  C. 
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Field  and  Laboratory  Studies  of  Soils.  By  Pro- 
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Field  and  Laboratory  Studies  of  Crops.  By  Pro- 
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The  Chemistry  of  Farm  Practice.  By  T.  E.  Keitt, 
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5000  4-2-17 


THE   CHEMISTRY   OF 
FARM  PRACTICE 


BY 


T.  E.  KEITT 

Cfiemist  of  South  Carolina  Expenment  Station,  and  I't-qfessor  of  Soils, 
Clemson  Agricultural  College,  Clernson  College,  S.  C. 


FIRST  EDITION 
FIRST  THOUSAND 


NEW  YORK 

JOHN  WILEY  &  SONS,  Inc. 
London:   CHAPMAN  &  HALL,  Limited 
1917 

J1'19 


Copyright,  1917 

BY 

T.  E.  KEITT 


PRESS    OF 

BRAUNWORTH    &    CO. 

3I>OK    MANUFACTURERS 

BROOKLYN.  N.  Y. 


PREFACE 


LiFK,  food,  and  raiment  are  directly  or  indirectly  de- 
pendent upon  agricultural  products.  In  the  settlement  of 
our  country,  land  was  abundant  and  people  were  few,  con- 
sequently little  thought  was  given  to  the  needs  of  the 
increasing  numbers  of  succeeding  generations.  As  the  land 
first  cultivated  lost  its  fertility,  the  tide  of  population  turned 
westward  where  unlimited  areas  of  virgin  soil  awaited  the 
herds  and  plowshares  of  the  settlers.  But  this  fresh  area 
has  been  occupied,  and  to  maintain  the  fertility  of  those 
fields  that  are  still  productive  and  to  restore  those  that  have 
become  exhausted  is  the  problem  now  facing  agriculture. 

The  maintenance  of  the  fertility  of  a  productive  soil 
demands  the  intelligent  application  of  the  principles  of 
agricultural  chemistry.  Tlie  restoration  of  wornout  fields 
is  a  difficult  and  costly  undertaking.  The  successful  farmer 
must  reinforce  his  art  by  the  application  of  the  fundamental 
information  derived  from  the  study  of  chemistry,  geology, 
botany,  Imcteriology,  and  entomology. 

Chemistry  aids  agriculture  in  many  ways.  By  means 
of  it,  exact  data  are  collected  and  the  fundamental  reasons 
for  practical  results  are  explained.  Then,  too,  chemistry 
invents  new  or  improves  old  methods  of  fertilization.  The 
chemist  analyzes  soils,  manures  and  vegetable  products. 
The  value  of  soil  analysis  to  the  practical  farmer,  perhaps 
formerly  overrated,  in  more  recent  years  has  been  under- 
rated. From  a  soil  analysis  the  farmer  can  at  least  learn 
if  his  soil  is  unusually  deficient  in  any  important  element. 
Chemistry  also  protects  the  agriculturist  from  the  impositions 
of  the  unscrupulous  fertiHzer  manufacturer. 

The  thorough  analysis  of  farm   products  enables  the 


iv  PREFACE 

farmer  to  know  their  composition,  and  how  much  of  each 
element  they  contain.  This  analysis  serves  a  two-fold 
purpose:  First,  the  composition  of  a  plant  shows  what 
elements,  and  what  quantity  of  each,  have  been  removed 
from  the  soil.  This,  in  turn,  determines  what  the  soil 
must  contain  to  grow  plants  in  a  healthy  condition.  Second, 
in  feeding  vegetable  products  to  hvestock,  the  composition 
of  these  vegetables  must  be  known  in  order  that  the  rations 
may  be  compounded  correctly. 

Furthermore,  chemistry  explains  how  plants  grow  and 
are  nourished.  It  shows  the  kind  and  the  quantitj-^  of 
foods  which  plants  require  at  various  stages  of  their  growth, 
and  this  guides  the  farmer  in  properly  handling  his  crops. 
It  teaches  what  purposes  the  different  elements  in  the  food 
supphed  serve  in  animal  economy  and  how  the  best  results 
in  animal  feeding  may  be  obtained  with  the  least  outlay 
of  time,  labor,  and  expense. 

The  purpose  of  this  text  is  to  furnish  the  knowledge  of 
the  fundamentals  of  chemistry  required  for  intelligent 
agriculture  and  to  apply  this  knowledge  to  the  art  of 
agriculture  and  to  the  problems  of  the  agriculturist.  No 
attempt  has  l^een  made  to  limit  its  scope  to  the  study  of 
soils,  fertihzers,  and  manures,  although  these  subjects  are 
given  careful  consideration.  In  addition,  such  subjects  as 
feeds,  nutrition,  sanitary  water,  boiler  water,  and  insecti- 
cides, subjects  in  which  not  only  the  farmer,  but  the  sub- 
urban resident  is  interested — are  discussed  in  as  non- 
technical language  as  possible. 

The  student  of  this  book  is  urgently  requested  to  make 
a  careful  study  of  the  first  chapters;  for  in  them  has  been 
given  in  as  concise  and  elementary  form  as  is  practicable 
the  chemistry  applied  in  the  chapters  which  follow.  Each 
succeeding  chapter  requires  a  knowledge  of  the  preceding 
chapter,  consequently  they  should  be  studied  in  sequence. 

The  author  wishes  to  express  here  his  indebtedness 
to  Professor  Charles  M.  Allen,  Pratt  Institute,  for  careful 


PREFACE  V 

revision  of  the  chapters  on  General  Chemistry  and  the 
critical  reading  of  the  whole  text,  and  to  Dr.  C.  A.  Peters, 
Amherst  Agricultural  College,  for  many  helpful  sugges- 
tions and  criticisms.  Acknowledgment  is  made  to  Mr.  J. 
Ross  Hanahan  of  Planters'  Fertilizer  Company  for  Figs. 
37,  38  and  39,  to  Mr.  John  S.  Carroll  of  the  German  KaU 
Company  for  Figs.  40,  41  and  42  and  52-60,  and  to  Dr. 
Wm.  S.  Myers  of  the  Chilean  Nitrate  Propaganda  for  Figs. 
45-51.  The  following  members  of  the  faculty  of  Clemson 
College  furnished  photographs:  Director  J.  N.  Harper,  Dr. 
F.  H.  H.  Calhoun,  Prof.  W.  A.  Thomas,  and  Mr.  F.  G. 
Tarbox.  Mr.  T.  C.  Hough  furnished  valuable  aid  by  mak- 
ing drawings.  Director  Thome  of  the  Ohio  Experiment 
Station  and  Director  Hartwell  of  the  Rhode  Island  Experi- 
ment Station  very  kindly  gave  permission  for  the  repro- 
duction of  cuts  used  to  illustrate  bulletins  of  their  respective 
stations.  Cuts  from  Farmers'  Bulletins  of  the  United  States 
Department  of  Agriculture  were  reproduced  as  well  as  cuts 
from  bulletins  of  the  South  Carolina  Experiment  Station. 

Standard  books  that  bear  on  the  subject  have  been 
freely  consulted.  Grateful  acknowledgment  is  also  due 
my  father,  Thomas  W.  Keitt,  for  valuable  assistance  in 
reading  proof. 

T.  E.  Keitt. 

Clemson  College,  1916. 


EDITOR'S   NOTE 


This  little  text  has  been  prepared  in  the  belief  that 
boys  attending  high  schools  in  farming  communities  and 
those  taking  short  courses  in  agricultural  colleges  should 
receive  instruction  in  the  chemistry  applying  to  farm  prac- 
tice. For  such  students,  there  is  neither  time  nor  oppor- 
tunity for  the  usual  formal  course  in  General  Chemistry, 
followed  by  technical  Agricultural  Chemistry.  A  single 
elementary  course  combining  the  two  is  possible,  in  which 
the  information  furnished  is  definite,  practical  and  reason- 
ably adequate. 

In  such  a  combined  com-se,  the  essential  principles  of 
Chemistry  naturally  come  first,  to  be  followed  by  their 
applications  to  the  problems  which  arise  in  the  life  on  a 
farm,  in  the  growing  of  farm  crops,  or  in  the  feeding  and  care 
of  farm  animals.  This  order  has  been  followed  by  the  author 
in  the  present  text.  It  is  believed  that  teachers  in  high 
schools  attended  by  boys  living  on  farms  and  in  agricultural 
colleges  giving  short  courses  will  find  in  The  Chemistry  of 
Farm  Practice  the  text-book  best  suited  to  their  needs. 
It  should  prove  especially  valuable,  also,  as  a  reference 
book  for  those  interested  in  farming. 

The  Editor. 


TABLE  OF  CONTENTS 


CHAPTER  I 


Elements,  Atomic  Weights,  Molecules,  Symbols,  Molecular 

Weights,  Oxidation,  Reduction 1 

Chemistry — Elements — Composition  of  Matter — Atomic 
Weights  —  Molecules  of  Elements  —  Symbols  —  Molecular 
Weights — Oxidation — Combustion — Kindling  Temperature — 
Spontaneous  Combustion — Reduction. 

CHAPTER  II 

Compounds,  Mixtures,  Valence,  Formulas  and  Equations        13 
Conservation  of  Matter — Compounds — Mixtures — Valence 
— Formulas — Hydrates — Criss-cross  Rule — Equations. 

CHAPTER  III 

Acids,  Bases,  Salts,  Anhydrides,  Dissociation,  and  Nomen- 
clature      24 

Groups  of  Elements — Classes  of  Compounds — Acids — Bases 
— Salts — Anhydrides — Dissociation — Nomenclature  of  Com- 
pounds. 

CHAPTER  IV 

The  Elements  Necessary  for  Plant  Growth 32 

Oxygen  —  Hydrogen  —  Carbon  —  Nitrogen  —  Phosphorus 
— Sulphur — Potassium — Calcium — Magnesium — Iron. 

CHAPTER  V 

Water,  Springs,  Wells,  Hardness  and  Household  Water  ....     44 
Properties  of  Water — Solvent  Action  of  Water — Availability 
of  Plant  Food — Drinking  Water — Hardness  in  Water — Fil- 
tered Water — Boiled  Water — Distilled  Water — Boiler  Water. 


TABLE  OF  CONTENTS 


CHAPTER  VI 

Soil  Water 59 

Water  Requirements  of  Plants — Soil  Components — Soil 
Water. 

CHAPTER  VII 

Air  in  Soils 63 

Composition  of  the  Atmosphere — Soil  Air — Effect  of  Car- 
bon Dioxide  on  Decay — Oxygen  Must  be  Present — Factors 
Affecting  Soil  Air — Means  of  Producing  a  Change  of  Soil  Air. 

CHAPTER  VIII 

The  Assimilation  of  Plant  Food 70 

Sources  of  Plant  Food — Osmosis — Function  of  the  Leaves 
of  Plants — Leaching. 

CHAPTER  IX 

The  Formation,  Composition,  and  Fertility  of  Soils 76 

Formation  of  Soil — Composition  of  Soils — Gain  and  Loss 
of  Plant  Food — Importance  of  the  Rotation  of  Crops — 
Proper  Sequence  of  Crops — Use  of  Manures — Keeping  the 
Land  Covered. 

CHAPTER  X 

Animal  Manures 92 

Quality — Liquid  Manures — Rotted  Manures — Effect  of 
Exposure  to  the  Weather — Rate  of  Application. 

CHAPTER  XI 

Agricultural  Lime 97 

Sources  of  Lime — Effects  of  Lime  on  the  Soil — Shipping 
Lime — Applying  Lime  to  the  Soil — Machine  for  Applying 
Lime — Gypsum . 

CHAPTER  XII 

Phosphorus 107 

Presence  in  the  Soil — Commercial  Sources — Phosphate 
Rock — Acid  Phosphate  or  Super  Phosphate — Thomas  Phos- 
phate or  Basic  Slag — Bone — Mineral  Phosphate — Guano — 
Purchase  and  Application  of  Phosphorus. 


TABLE  OF  CONTENTS  XI 

PAGE 

CHAPTER  XIII 

Nitrogen 120 

Importance  of  Nitrogen — Commercial  Nitrogen  Profitable 
— Selection  of  Source  of  Nitrogen — Inorganic  Sources  of 
Nitrogen — Saltpeter — Sodium  Nitrate — Calcium  Nitrate — 
Ammonium  Sulphate — Organic  Sources  of  Nitrogen — Vege- 
table Sources. 

CHAPTER  XIV 

Sources  and  Use  of  Potash  Salts 137 

Occurrence — Wood  Ashes — Organic  Sources  of  Potash — 
Minor  Sources — Commercial  Salts  of  Potash — Functions  of 
Potash — Use  of  Potash  on  Different  Soils — Selection  of  the 
Source  of  Potash — Tendency  to  Use  too  Much  Potash. 

CHAPTER  XV 

Measuring  Plant  Food  Requirements 152 

Forms  of  Plant  Food — Soil  Analyses — Field  Tests. 

CHAPTER  XVI 

Mixing  of  Fertilizers 162 

Advantages  of  Home  Mixing — The  Calculation  of  Formulas. 

CHAPTER  XVII 

Animal  Nutrition 174 

Purposes  of  Animal  Food — Classes  of  Foods — Development 
of  the  Science  of  Animal  Nutrition — Digestible  Nutrients — 
Metabohsm — Rations  for  Various  Purposes. 

CHAPTER  XVIII 

Feeds  and  the  Calculation  of  Rations 184 

Corn  —  Oats  —  Barley  —  Dried  Brewers'  Grain  —  Rye — 
Wheat  —  Rice  —  Cottonseed  Meal  —  Linseed  Meal  —  Meat 
Scraps — Dried  Fish — Blood  Meal — Soy-bean  Meal — Pea- 
nuts— Timothy — Cereals — Legumes — Composition  and  Diges- 
tibiUty  of  Feeds — The  Calculation  of  Rations. 

CHAPTER  XDC 

Milk  and  Its  Products 198 

Milk — Danger  from  Infected  Milk — Preservatives — The 
Detection  of  Formaldehyde  in  Milk — Detection  of  Boracic 
Acid — Testing  Milk  for  Per  Cent  of  Fat — Determination  of 
Specific  Gravity — Ash — Butter — Cheese — Condensed  Milk. 


Xii  TABLE  OF  CONTENTS 


CHAPTER  XX 

Insecticides,  Fungicides  and  Disinfectants 212 

Two  Classes  of  Injurious  Insects — Injurious  Fungi — 
Insecticides  for  Biting  Insects — Insecticides  for  Sucking 
Insects — Fungicides — Common  Disinfectants . 

CHAPTER  XXI 

Paints  and  Whitewashes 225 

Paints — Drying  Oils  —  Driers — White  Pigments — Green 
Pigments — Blue  Pigments — Red  Pigments — Yellow  Pigments 
— Brown  Pigments — Black  Pigments — Mixing  Paints — White- 
washes— Calcimine — Varnishes — Shellac — Glue. 

CHAPTER  XXII 

Materials  Producing  Heat  and  Light.    Fire  Extinguishers  233 
Petroleum — Kerosene — Gasohne — Acetylene — Fire  Extin- 
guishers. 

CHAPTER  XXIII 

Concrete 239 

Use — Cement  Manufacture — Setting  of  Cement — Sand — 
Gravel — Quantity  of  Material  for  Different  Mixtures — Mix- 
ing Concrete — Placing  the  Concrete, 


THE  CHEMISTRY  OF  FARM  PRACTICE 


CHAPTER  I 

ELEMENTS— ATOM IC  WEIGHTS— MOLECULES— SYM BOLS— 
MOLECULAR  WEIGHTS— OXIDATION— RED^^ICTION 

1.  Chemistry.  Chemistry  deals  with  the  composition 
and  properties  of  substances  and  the  changes  which  sub- 
stances undergo.  Agricultural  chemistry  has  to  do  with 
the  application  of  the  knowledge  gained  through  chemistry 
to  the  art  of  agriculture  and  to  the  problems  which  the 
farmer  has  to  solve.  To  understand  agricultural  chemistry 
we  must  gain  first  a  knowledge  of  some  of  the  underlying 
principles  of  General  Chemistry. 

2.  Elements.  Matter  is  made  up  either  of  simple  ele- 
ments or  of  these  elements  combined  into  compounds  of 
unvarying  composition.  An  element  is  a  simple  substance 
which  has  certain  definite  properties  and  which  has  not 
been  separated  into  substances  having  different  properties. 
Iron  is  an  element.  However  minutely  the  piece  of  iron 
may  be  divided,  the  smallest  particle  will  always  have 
properties  identical  with  the  iron  before  its  division. 

Somewhat  more  than  eighty  elements  have  been  isolated 
which  have  resisted  all  the  attempts  of  present  chemical 
methods  at  further  separation.  Each  element  has  certain 
distinctive  properties  that  prevent  it  being  classed  with 
other  elements,  although  certain  elements  which  are  closely 
related  have  sonie  of  their  properties  in  common. 

Only  ten  elements  are  necessary  to  sustain  the  life  of 


2  CHEMISTRY  OF  FARM  PRACTICE 

the  growing  plant;  these  are  carbon,  hydrogen,  oxygen, 
nitrogen,  phosphorus,  sulphur,  potassium,  magnesium,  cal- 
cium and  iron.  Some  of  these  elements  are  derived  from 
the  atmosphere,  some  from  water  and  some  from  the  soil. 
Most  of  the  substances  of  plants  consist  of  the  elements, 


OXYGEN 
49.8S< 

SILICON 

26.1$« 

ALUMINIUM  7.3S« 

IRON  4.W 

CALCIUM  3.2sf 

SODIUM  2.3?« 

POTASSIUM  2.35« 

MAGNESIUM  2.2?f 

ALL  OTHER  ELEMENTS  2.75^ 

Fig.  1. — Percentage  of  elements  in  the  combined  mass  of  atmosphere, 
waters  and  crust  of  the  earth. 


carbon,  hydrogen,  and  oxygen,  which  are  obtained  from 
the  atmosphere,  or  from  water.  Nitrogen  is  the  most 
expensive  and  the  most  elusive  of  the  elements  required 
by  plants.  A  part  of  the  nitrogen  may  be  derived  from 
the  atmosphere  by  certain  plants  under  conditions  we 
shall  study  later,  but  most  of  the  nitrogen  which  serves  as 


ELEMENTS— ATOMIC  WEIGHTS— MOLECULES,  ETC.      3 

plant  food  comes  from  the  decomposition  of  organic  sub- 
stances in  the  soil.  The  other  six  elements  necessary  for 
plant  growth  are  required  in  comparatively  small  amounts. 
With  the  exception  of  phosphorus,  soils  usually  contain 
an  abundant  supply  of  these  "  ash  elements." 

In  the  diagram,  Fig.  1,  is  shown  the  relative  propor- 
tion of  eight  of  the  most  abundant  of  the  elements  as  found 
in  the  atmosphere,  all  waters,  and  the  solid  parts  of  the 
earth's  crust  which  have  been  examined.  It  will  be  noticed 
that  the  seventy-five  elements  not  mentioned,  altogether, 
comprise  but  2.7  per  cent  of  the  earth's  constituents.  With 
the  exception  of  a  comparatively  small  quantity  of  ox3'gen 
existing  in  a  free  condition  in  the  air,  this  figure  represents 
the  percentage  of  the  elements  as  they  exist  in  compounds. 

3.  Composition  of  Matter.  Matter  may  be  divided  and 
subdivided  till  definite  parts  called  molecules  are  reached. 
Finally  the  molecule,  by  chemical  means,  may  be  separated 
into  invisible  particles  called  atoms.  The  atom  may  be 
defined  as  the  extremely  minute  particle  of  matter  that 
enters  as  a  unit  into  chemical  combinations  with  other 
atoms.  A  molecule  is  the  smallest  part  of  matter  that  can 
exist  by  itself.  An  atom  does  not  remain  free  or  uncom- 
bined;  it  unites  either  with  other  atoms  of  the  same  kind 
to  form  a  molecule  of  an  element  or  it  combines  with  atoms 
of  a  different  kind  and  thus  produces  a  compound. 

4.  Atomic  Weights.  Atoms  combine  chemically  accord- 
ing to  definite  proportion  by  weight.  The  smallest  amount 
of  hydrogen  that  will  enter  into  chemical  reaction,  i.e., 
the  hydrogen  atom,  is  less  by  weight  than  the  atom  of 
any  other  element.  For  this  reason  hj-drogen  may  be 
taken  as  a  convenient  unit  of  comparison  and  its  smallest 
combining  weight,  which  is  the  weight  of  its  atom,  may 
be  assumed  to  be  one.  The  gases  hydrogen  and  chlorine, 
when  mixed  and  exposed  to  light,  will  form  a  new  substance, 
hydrogen  chloride,  which  in  its  water  solutib^h  is  called 
hydrochloric  acid.     When  one  part  bj'  weight' of  hydrogen 


4  CHEMISTRY  OF  FARM  PRACTICE 

is  allowed  to  unite  with  an  excess  of  chlorine,  it  is  found 
that  it  will,  in  every  case,  combine  with  35.46  times  its 
own  weight  of  the  chlorine.  Hydrogen  chloride  therefore 
contains  hydrogen  and  chlorine  in  the  proportion  of  1 
to  35.46.  There  are  reasons  for  believing  that  the  mole- 
cule of  hydrogen  chloride  consists  of  one  atom  of  hydrogen 
combined  with  one  atom  of  chlorine.  If  this  is  true,  then, 
taking  the  hydrogen  atom  as  a  unit  of  weight,  the  chlorine 
atom  weighs  35.46  and  the  molecule  of  hydrogen  chloride, 
HCl,  weighs  36.46.  It  has  been  foimd  that  the  elements 
which  compose  a  compound  always  combine  in  propor- 
tion to  their  atomic  weights  or  to  some  multiple  of  their 
atomic  weights.  It  will  be  seen  that  this  must  be  the 
case  if  an  atom  is  indivisible. 

The  atomic  weight  of  an  element  is  fixed  by  deter- 
mining with  great  care  the  weight  of  the  element  that  will 
unite  with  another  element  whose  atomic  weight  has  pre- 
viously been  determined.  As  nearly  all  the  elements  form 
compounds  with  oxygen,  while  comparatively  few  unite 
with  hydrogen,  the  atom  of  oxygen  with  an  assigned  weight 
of  16  is  really  used  as  the  standard  instead  of  the  atom 
of  hydrogen,  which  it  will  be  observed  in  the  table  on  page 
6,  weighs  1.008. 

5.  Molecules  of  Elements.  The  common  elementary 
gA333,  such  as  oxygen,  hydrogen,  nitrogen,  and  chlorine, 
have  molecules  consisting  of  two  atoms  of  each  element. 
The  molecules  of  some  of  the  elements,  such  as  phosphorus, 
arsenic,  and  antimony,  have  four  atoms  in  each  molecule, 
when  they  are  at  a  temperature  slightly  above  vaporiza- 
tion. In  most  cases  the  number  of  atoms  in  a  molecule 
of  an  element  depends  upon  its  temperature.  Thus  sul- 
phur vapor  at  468°  C.  has  eight  atoms  to  the  molecule;  at 
830°  C.  its  molecule  has  but  two  atoms. 

Some  elements,  such  as  sodium,  potassium,  mercury, 
and  zinc,  when  in  a  vaporous  state,  have  but  one  atom 
to  each  molecule.     Such  molecules  differ  from  atoms  in 


ELEMENTS— ATOMIC  WEIGHTS— MOLECULES,  ETC.      5 

that  they  seem  to  have  lost  the  chemical  affinities  which 
are  characteristic  of  atoms.  The  number  of  atoms  in  a 
molecule  of  an  element  when  it  is  in  the  solid  condition 
is  not  known. 

6.  Symbols.  For  the  sake  of  convenience,  each  element 
is  represented  by  one  or  more  letters.  This  abbreviation 
of  the  name  of  an  element  is  called  its  symbcl.  The  letter 
used  to  represent  an  element  is  often  the  first  letter  of  its 
name.  It  is  written  as  a  capital,  but  unhke  other  abbre- 
viations, it  is  not  followed  by  a  period.  The  symbol  of 
oxygen  is  O,  of  hydrogen  is  H,  of  nitrogen  is  N,  and  P 
is  the  symbol  of  phosphorus.  When  the  name  of  more 
than  one  element  begins  with  the  same  letter,  the  most 
important  or  the  first  discovered  of  these  elements  has  the 
single  letter  for  a  sj'mbol  and  to  the  others  an  additional 
letter  is  assigned.  Thus  C  is  the  symbol  for  carbon,  Ca 
the  symbol  for  calcium,  CI  the  symbol  for  chlorine,  Cr  for 
chromium.  It  will  be  noted  that  the  second  letter  is  not 
written  as  a  capital.  Sometimes  the  symbol  is  derived  from 
the  foreign  word  which  means  the  element,  as  Fe  from 
the  Latin  ferrwn,  meaning  iron,  K  from  Kalium,  the  Ger- 
man word  meaning  potash,  which  contains  potassium, 
Hg  from  the  Greek,  hydrargyrum,  meaning  "  water  silver," 
a  good  description  of  mercury.  Many  symbols  are  taken 
from  the  names  of  countries,  as  Cu,  copper,  from  the  island 
bf  Cyprus,  Mg,  magnesium,  from  Magnesia  in  Asia 
Minor.  The  symbol  of  an  element  represents  not  only 
the  name  of  the  element,  but  it  means  also  one  atom  of 
the  element  and  consequently  is  a  definite  weight.  S 
stands  not  only  for  sulphur,  but  for  one  atom  of  sulphur, 
which  weighs  32,  or  two  times  the  weight  of  an  atom  of 
the  standard,  oxygen. 

7.  Molecular  Weights.  One  method  for  determining 
molecular  weights  depends  upon  an  hypothesis  proposed 
by  Avogadro,  which  has  been  quite  universally  accepted. 
This  hypothesis  states  that  "  under  the  same  conditions 


CHEMISTRY  OF  FARM  PRACTICE 


:i. 


TABLE   I— THE   COMMON   ELEMENTS 


Elements. 


Aluminium . 
Antimony . 
Arsenic. .  .  . 
Barium.  .  . 
Bismuth. . . 

Boron 

Bromine. . . 
Calcium. .  . 
Carbon. .  .  . 
Chlorine. .  . 
Chromium. 
Cobalt .... 
Copper. .  . . 
Fluorine. .  . 

Gold 

Hydrogen . 
Iodine.  .  .  . 

Iron 

Lead 

Lithium. .  . 
Magnesium 
Manganese 
Mercury.  . 
Nickel .... 
Nitrogen.  . 
Oxygen .  .  . 
Phosphorus 
Platinum. . 
Potassium . 
Radium.  . . 
Silicon .... 

Silver 

Sodium .  .  . 
Sulphur . . . 

Tin 

Zinc 


Symbols. 

Atomic  Weights 

Usual  Valence. 

Al 

27.1 

3 

Sb 

120.2 

3  or  5 

As 

74.96 

3  or  5 

Ba 

137.37 

2 

Bi 

208.0 

3 

B 

11.0 

3 

Br 

79.92 

1 

Ca 

40.07 

2 

C 

12.0 

4 

CI 

35.46 

1 

Cr 

52.0 

3 

Co 

58.97 

2 

Cu 

63.57 

2 

F 

19.0 

1 

Au 

197.2 

3 

H 

1.0C8 

1 

I 

126.92 

1 

Fe 

55.84 

2  or  3 

Pb 

207.1 

2 

Li 

6.94 

1 

Mg 

24.32 

2 

Mn 

54.93 

2,  4  or  6 

Hg 

200.6 

1  or  2 

Ni 

58.68 

2  or  3 

N 

14.01 

3  or  5 

0 

16.0 

2 

P 

31.04 

3  or  5 

Pt 

195.2 

2  or  4 

K 

39.1 

1 

Ra 

226.4 

2 

Si 

28.3 

4 

Ag 

107.88 

1 

Na 

23.0 

1 

S 

32.07 

2 

Sn 

119.0 

2  or  4 

Zn 

65.37 

2 

ELEMENTS— ATOMIC  WEIGHTS— MOLECULES,  ETC.       7 

of  temperature  and  pressure,  all  gases  have  the  same  number 
of  molecules  in  equal  volumes."  While  it  is  quite  impos- 
sible to  isolate  and  weigh  a  single  molecule,  yet  if  we  select 
as  a  standard  of  molecular  weight  a  molecule  of  oxygen, 
consisting  of  two  atoms,  and  assign  to  it  a  weight  of  32, 
we  may,  by  assuming  the  Avog^dro  hypothesis,  obtain 
the  weight  of  the  molecule  of  any  gas.  This  is  done  in 
the  case  of  ammonia  by  weighing  equal  volumes  of  ammonia 
and  of  oxygen  under  the  same  conditions  of  temperature  and 
of  pressure,  and  solving  for  the  molecular  weight  of  ammonia 
in  the  proportion: 

Weight  of  volume  of  oxygen  :  weight  of  same  volume  of 

ammonia  =  32  :  molecular  weight  of  ammonia. 

In  this  manner  we  may  determine  accurately  the  weight 
of  the  molecule  of  any  element  or  of  any  compound  which 
may  be  weighed  in  a  gaseous  condition. 

8.  Oxidation  and  Reduction.  An  understanding  of  the 
principles  of  chemistry  involved  in  the  processes  of  oxidation 
and  of  reduction  is  important.  It  is  impossible  to  obtain 
a  working  knowledge  of  chemistry  without  gaining  a  mastery 
of  these  processes.  A  simple  case  of  oxidation  takes  place 
when  a  bright  strip  of  iron  is  heated  over  a  flame.  The 
oxygen  of  the  air,  more  active  at  the  high  temperature, 
combines  with  the  metallic  iron,  rusting  it  into  a  black 
oxide  of  ion.  If  a  silver  spoon  is  exposed  to  the  fumes 
of  sulphur,  the  silver  combines  with  the  sulphur  and  black 
silvsr  sulphide  is  formed  on  the  surface  of  the  metal.  This 
is  also  a  case  of  oxidation,  although  here  there  is  no  oxygen 
involved. 

Oxidation  may  be  defined  as  the  combination  of  oxygen, 
or  of  other  elements  that  act  chemically  in  the  same  way 
as  oxygen,  with  other  material.  Sometimes  oxidation  takes 
place  in  two  or  more  stages.  Thus  metallic  mercury  will 
be  oxidized  by  combining  with  one  atom  of  chlorine,  form- 
ing white  mercurous  chloride  or  calomel,   which,   in  turn, 


8 


CHEMISTRY  OF  FARM  PRACTICE 


may  be  further  oxidized  by  adding  to  itself  another  atom 
of  chlorine,  forming  mercuric  chloride  or  corrosive  sub- 
limate. 

9.  Combustion.  Oxidation  produces  heat  as  a  result 
of  the  chemical  action  taking  place.  Should  oxidation  be 
sufficiently  rapid  to  produce  enough  heat  so  that  light  is 
evolved,  the  process  is  termed  combustion.  When  the 
materials  entering  into  combustion  are  gases,  a  flame  is 
produced.  Burning  wood  is  undergoing  combustion,  this 
process  of  oxidation  being  supported  by  the  oxygen  drawn 
from  the  atmosphere  entering  into  rapid  union  with  the 
hydro-carbon  gases  produced  from  the  heated  wood.  The 
three  conditions  necessary  for  combus- 
tion are  first,  a  combustible  substance; 
second,  a  supporter  of  combustion; 
third,  a  kindling  temperature.  Usually 
carbon  or  hydrogen  or  some  of  their 
numerous  compounds  or  the  metals  that 
are  easily  oxidized  are  regarded  as  the 
combustibles,  while  oxygen  or  some  of 
the  elements  that  act  chemically  like 
oxygen  are  considered  the  supporters  of 
combustion.  The  material  entering  into 
chemical  reaction  which  is  the  more 
abundant  is  likely  to  be  considered  the 
supporter  of  combustion,  and  thus  the 
combustible  and  the  supporter  of  com- 
bustion may  exchange  places. 

This  is  seen  in  the  reversal  of  flames 
Fig.  2.— Apparatus    effected  by  the  apparatus  in  Fig.  2.     The 

s  owing    re-    j^mp  chimney  is  fitted  with  corks  and  tubes 
versal  of  names.  •      ^      ^  •  i       i 

as  m  the  figure.     The  straight  glass  tubes 

at  A  and  C  are  at  least  ye  of  ^^  i^^ch  in  internal  diameter. 

The  glass  elbow  D  is  connected  with  the  illuminating  gas 

supply.     While  the  finger  is  placed  at  C,  closing  the  tube, 

the  gas  is  turned  on  and  allowed  to  flow  till  the  chimney 


ELEMENTS— ATOMIC  WEIGHTS— MOLECULES,  ETC.      9 

is  surely  full  of  gas,  which  is  escaping  at  A.  The  gas  at  A 
is  now  ignited  and  the  gas  cock  turned  down  till  a  small 
inverted  flame  is  produced  at  A.  The  finger  is  now  removed 
from  C  and  the  flame  at  A  will  be  seen  to  ascend  the  tube 
and  to  burn  at  B.  The  gas  issuing  at  C  is  immediately 
ignited.  If  we  consider  these  two  flames,  we  shall  see 
that  the  one  at  C  is  composed  of  illuminating  gas  burning 
in  an  atmosphere  of  air,  and  naturally  the  oxygen  of  the 
air  would  be  considered  the  supporter  of  combustion, 
while  the  gas  would  be  considered  the  combustible.  The 
flame  at  B  is  composed  of  air  coming  up  the  tube  from  A 
which  is  burning  in  an  atmosphere  of  illuminating  gas, 
and  in  this  case  we  should  naturally  consider  the  illuminating 
gas  as  the  supporter  of  the  combustion  while  the  oxygen 
of  the  air  is  the  combustible. 

10.  Kindling  Temperature.  While  oxidation  may  take 
place  at  any  temperature,  in  order  to  start  and  to  con- 
tinue combustion,  it  is  necessary  for  the  combustible  and 
the  supporter  of  combustion  to  be  at  a  certain  tempera- 
ture, known  as  the  kindling  temperature.  Each  substance, 
under  the  same  conditions,  has  its  own  definite  kindling 
temperature.  Phosphorus  has  a  very  low  kindling  tem- 
perature, taking  fire  spontaneously  in  the  air.  This  is  due 
to  the  fact  that  oxidation  raises  the  temperature  of  the 
phosphorus  to  its  kindling  point.  If  a  bit  of  phosphorus 
as  large  as  a  wheat  grain  is  dissolved  in  a  small  amount 
of  carbon  disulphide  and  the  solution  poured  upon  a  filter 
paper  placed  in  an  iron  ring,  as  soon  as  the  carbon  disulphide 
evaporates,  the  phosphorus  will  burst  into  flame.  In  this 
case  the  finely  divided  condition  of  the  phosphorus  exposes  a 
relatively  large  surface  to  oxidation.  When  a  candle  flame 
is  extinguished  by  blowing  upon  it,  the  blast  of  air  cools 
the  flame  below  its  kindling  point. 

The  quantity  of  heat  produced  by  combustion  will  de- 
pend upon  the  quantity  and  the  character  of  the  gases 
entering  into  reaction,  while  the  degree  of  heat  will  depend 


10  CHEMISTRY  OF  FARM  PRACTICE 

upon  the  nature  of  the  combining  substances  and  upon 
how  intimately  the  combustible  and  supporting  gases  may 
be  mixed  at  the  point  of  ignition.  Hence  a  blast  is  used 
to  provide  a  large  quantity  of  oxygen  which  is  introduced 
into  the  interior  of  the  combustible  gas,  which  is  then 
forced  to  combine  internally  with  the  air  of  the  blast  and 
externally  with  the  oxygen  of  the  at- 
mosphere. The  hole  near  the  base  of 
the  Bunsen  burner,  Fig.  3,  is  required 
to  supply  air  for  combustion.  The 
blacksmith's  forge,  Fig.  4,  must  be 
equipped  with  a  "  blower  "  to  furnish 
admit  Air  euough  air  for  the  complete  combustion 

^"THRB         of  the  large  amount  of  gas. 
^^^^gNGas  Intake  jj^    mauy  cases  the  oxidation    is    a 

^tiij^MP^  slow  process.     This  may  be  seen  in  the 

rusting  of  iron,  the  tarnishing  of  copper, 
burner  ^^^  dulling  of  zinc.     When  ink   that  is 

pale  when  first  applied  becomes  dark 
upon  exposure,  the  ink  has  undergone  oxidation.  When 
paper  turns  yellow  with  age,  it  is  being  slowly  oxidized. 
Almost  everything  we  see  about  us  has  been  oxidized. 
Besides  the  noble  metals,  such  as  gold  and  platinum,  it 
is  only  those  substances  that  have  been  artificially  deprived 
of  their  oxidizing  constituent  that  exist  in  any  other  than 
an  oxidized  condition. 

The  rapidity  with  which  oxidation  takes  place  does  not 
affect  the  total  quantity  of  heat  produced.  An  iron  wire 
may  be  burned  in  a  jar  of  oxygen  and  the  combustion  may 
last  but  a  few  seconds,  or  the  wire  may  be  rusted  by  exposure 
to  moist  air,  and  the  oxidation  may  take  a  month  to  complete 
itself,  but  when  the  two  actions  are  complete,  if  the  same 
iron  oxide  is  finally  produced  and  in  the  same  quantity, 
the  total  amount  of  heat  will  be  identical  in  the  two  cases. 
Although  combustion  cannot  take  place  without  light, 
yet  light  may  be   produced   by   other  means  than   com- 


ELEMENTS— ATOMIC  WEIGHTS— MOLECULES,  ETC.     11 

bustion,  as  in  the  case  of  the  carbon  filament  of  an  electric 
light  bulb. 

11.  Spontaneous  Combustion.  If  the  heat  produced  in 
slow  oxidation  is  not  allowed  to  be  dissipated,  the  tem- 
perature of  the  combustible  which  is  being  oxidized  may 
gradually  be  raised  till  it  attains  its  kindHng  temperature 


Blower  to 
Supplj  Air 


Fig.  4. — A  down-draft  forge. 


and  it  will  then  burst  into  flame.  This  is  quite  likely  to 
happen  in  the  case  of  vegetable  or  animal  oils  with  which 
cloths  may  have  been  saturated.  These  oils  are  "  drying 
oils,"  that  is,  they  are  easily  oxidized  as  shown  by  the 
necks  and  stoppers  of  their  containers,  which  are  gummed 
upon  standing.  This  combustion  is  produced  spontane- 
ously, that  is,  by  the  internal  development  of  heat  without 


12  CHEMISTRY  OF  FARM  PRACTICE 

the  action  of  an  external  agent  other  than  the  Oxidizer. 
Heaps  of  finely  divided  coal  may  in  the  same  way  be  set 
on  fire  by  the  spontaneous  combustion  occasioned  by  the 
oxidation  of  their  sulphur  or  oil  content, 

12.  Reduction.  This  process  is  the  reverse  of  oxidation. 
It  is  the  subtraction  from  a  compound  of  oxygen  or  of  the 
element  which  plays  the  role  of  oxygen.  The  extraction 
of  the  common  metals  from  their  ores  is  a  process  of  re- 
duction. This  process  is  brought  about  by  subjecting  the 
material  to  be  reduced  to  certain  reducing  agents  which 
have  a  stronger  affinity  for  the  oxygen  part  of  the  compound 
than  does  the  metal  originally  combined  with  that  part. 
The  most  useful  of  these  reducing  agents  are  carbon,  in 
the  form  of  charcoal  or -qoal,  hydrogen  and  the  hydro-carbon 
compounds  and  certain  active  metals,  such  as  sodium  or 
aluminium.  Carbon  monoxide  gas,  which  needs  more 
oxygen  so  as  to  make  itself  into  carbon  dioxide,  a  more 
stable  compound,  is  a  very  valuable  reducing  agent.  In 
the  highly  heated  areas  of  the  blast  furnace  in  the  process 
of  iron  reduction,  the  carbon  monoxide  takes  away  the  oxy- 
gen of  the  iron  ore  and  leaves  metallic  iron. 


CHAPTER  II 

COMPOUNDS— MIXTURES— VALENCE— FORMULAS- 
EQUATIONS 


13.  Conservation  of  Matter.  Chemical  changes  neither 
create  nor  destroy  matter.  By  chemical  means  matter 
may  be  converted  into  new  forms  having  different  prop- 
erties, hut  the  total  weight  of  the  substances  before  chemical 
action  will  equal  the  total  weight  of  the  substances  after  the 


Fig.  5. — The  black  solid,   carbon,   combined  with  the  yellow  solid, 
sulphur,  forms  the  colorless  liquid  carbon  disulphide. 

action  has  been  completed.  Sulphur,  when  burning,  com- 
bines with  the  oxygen  of  the  air,  and  when  the  sulphur  is 
entirely  consumed,  the  weight  of  the  choking  fumes  of 
sulphur  dioxide  produced  will  exactly  equal  the  sum  of 
the  weights  of  the  sulphur  burned  and  the  oxygen  with 
which  it  combined. 

14.  Compounds.     Two   or  more   elements  when  chem- 
ically combined  form  compounds.     A  chemical  compound 

13 


14  CHEMISTRY  OF  FARM  PRACTICE 

is  composed  always  of  the  same  elements  combined  in 
the  same  proportion  by  weight.  A  compound  possesses 
properties  which  differ  from  those  of  the  elements  of  which 
it  is  composed.  Chemists  have  recognized  many  thousands 
of  compounds,  each  of  which  has  a  characteristic  set  of 
properties  which  is  constant  and  differs  from  that  of  other 
compounds. 

The  element  carbon,  a  black  solid,  will  combine  chem- 
ically under  certain  circumstances  with  the  yellow  sohd, 
sulphur,  and  form  a  compound,  carbon  disulphide,  which 
is  a  transparent  liquid  with  a  characteristic  odor,  and 
very  volatile  at  ordinary  temperatures.  The  formation 
of  compounds  is  due  to  the  chemical  attraction  existing 
between  the  atoms  of  the  elements  which  causes  them 
to  combine  to  form  the  molecules  of  the  compound. 

15.  Mixtures.  Two  or  more  substances  may  be  ever 
so  intimately  blended  together,  but,  if  no  chemical  com- 
bination takes  place,  there  is  no  compound  produced. 
Such  a  mingling  is  termed  a  miature.  A  mixture  differs 
from  a  compound  in  two  ways:  First,  it  possesses  the 
characteristic  properties  of  all  of  its  ingredients;  second, 
the  proportion  of  its  constituents  may  vary  each  time 
the  mixture  is  made.  In  this  respect  a  mixture  differs 
from  a  compound  in  which  the  percentage  content  of  its 
constituents  docs  not  vary. 

16.  Valence.  .  When  hydrogen  gas  is  mixed  with  chlorine 
gas  and  exposed  to  diffused  light,  it  is  found  that  hj^drogcn 
chloride,  a  compound  whose  molecules  consist  of  one  atom 
of  each  element,  is  produced.  While  the  reason  for  the 
affinity  between  atoms  of  hydrogen  and  of  chlorine  is  not 
known,  yet  there  is  some  kind  of  attraction,  possibly  elec- 
trical, which  draws  and  binds  these  atoms  together.  We 
may  imagine  that  each  hydrogen  atom  has  a  string  attached 
to  it  by  means  of  which  it  unites  itself  to  other  atoms.  The 
hydrogen  atom  seems  to  have  but  one  of  these  strings 
which  may  be  called  bonds  or  valences,  and  it  is    there- 


COMPOUNDS— MIXTURES— VALENCE,  ETC.  15 

fore  called  a  monad,  or  univalent  element.  The  chlorine 
atom  usually  acts  as  a  monad  and  we  may  picture  that, 
when  hydrogen  chloride  is  produced,  the  bond  of  a  chlorine 
atom  ties  itself  to  the  bond  of  a  hydrogen  atom,  thereby 
making  a  stable  molecule.  One  atom  of  chlorine  will 
combine  with  one  atom  of  potassium  to  form  a  molecule 
of  potassium  chloride.  The  potassium  atom  is  therefore 
univalent. 

The  atoms  of  some  elements  have  the  capacity  to  hold 
in  combination  two  atoms  of  a  univalent  element.  We 
may  think  of  such  elements  as  having  two  bonds  attached 
to  each  atom;  two  atoms  of  hydrogen  are  required  to  unite 
to  one  atom  of  oxygen  so  as  to  form  water,  therefore,  the 
valence  of  oxygen  is  two.  Oxygen  is  called  a  diad  or 
bivalent  element.  A  number  of  important  elements  are 
bivalent,  such  as  calcium,  magnesium,  and  zinc.  One 
atom  of  nitrogen  unites  with  three  atoms  of  hydrogen  to 
form  ammonia.  Therefore  nitrogen  in  this  case  is  a  triad 
or  trivatent  element.  Other  elements  usually  trivalent  are 
phosphorus  and  aluminium.  Carbon  as  indicated  by  the 
four  atoms  of  hydrogen,  which  unite  with  one  atom  of 
carbon  to  form  marsh  gas,  is  tetravalent. 

Sometimes  an  element  may  develop  one  valence  under 
one  set  of  conditions  and  a  different  valence  under  other 
conditions.  Hydrogen  never  changes  valence,  oxygen  prac- 
tically never,  and  the  same  is  true  of  some  of  the  metallic 
elements,  such  as  calcium,  sodium,  and  potassium.  When 
oxygen  combines  with  an  element  it  is  liable  to  develop 
in  that  element  an  increase  in  its  valence.  For  example, 
when  sulphur  unites  with  hydrogen  to  produce  the  ill- 
smelling  gas,  hydrogen  sulphide,  the  valence  of  the  sul- 
phur atom  is  two,  as  indicated  by  the  two  atoms  of  hydrogen 
which  it  requires.  When  sulphur  is  burned  in  air,  most 
of  the  resulting  compound  is  sulphur  dioxide,  the  two  oxygen 
atoms  of  the  compound  indicating  that  sulphur  has  four 
bonds;    in  this  action  a  small  amount  of  sulphur  trioxide 


16  CHEMISTRY  OF  FARM  PRACTICE 

is  produced  and  this  compound  with  its  three  oxygen 
atoms  shows  that  the  sulphur  atom  develops  six  bonds. 
In  the  table  of  elements  given  on  page  6  the  usual  valence 
of  each  element  is  given.  The  theory  of  valence  is  used 
with  advantage  in  fixing  in  the  mind  the  formulas  of  com- 
pounds. 

17.  Formulas.  The  attraction  existing  between  atoms 
binds  them  into  molecules.  These  may  be  represented  by 
formulas  which  are  made  up  of  a  combination  of  symbols. 
The  formula  HCl  denotes  one  atom  of  hydrogen  chemically 
combined  with  one  atom  of  chlorine.  It  also  indicates  a 
weight  of  hydrogen  chloride  equal  to  the  combined  weight 
of  its  atoms.  This  is  the  molecular  weight  and  is  equal 
to  1+35.46  or  36.46.  Two  molecules  of  hydrogen  chloride 
are  expressed  2HC1.  The  molecule  of  water  is  expressed  by 
the  formula  H2O,  indicating  two  atoms  of  hydrogen  united 
with  one  atom  of  oxygen.  A  molecule  of  sulphuric  acid 
is  H2SO4.  This  indicates  that  it  is  composed  of  two  atoms 
of  hydrogen,  one  of  sulphur,  and  four  of  oxygen.  Three 
molecules  of  sulphuric  acid  would  be  expressed  by  the 
term  3H2SO4.  In  this  latter  formula  there  are  in  all  six 
atoms  of  hydrogen,  three  of  sulphur,  and  twelve  of  oxygen. 
The  formula  2Ca3(P04)2  means  two  molecules  of  calcium 
phosphate.  The  two  molecules  contain  six  atoms  of  cal- 
cium, four  atoms  of  phosphorus,  and  sixteen  atoms  of 
oxygen.  It  will  be  seen  that  each  of  the  coefficients 
3  and  2  in  these  two  examples  multiplies  each  of  the  sym- 
bols following  it,  taken  as  many  times  as  is  indicated  by 
the  subscript  following  each  symbol.  Each  of  the  symbols 
within  the  parenthesis  is  in  turn  multiplied  by  the  sub- 
script following  the  parenthesis. 

18.  Hydrates.  Many  salts  are  loosely  combined  with 
water  to  form  hydrates;  thus,  when  copper  sulphate  is 
dissolved  in  water  and  the  water  is  slowly  evaporated  there 
will  form  blue  crystals  which  contain  five  hydrating  mole- 
cules, and  this  formula  of  the  resulting  blue  vitriol  is  written 


COMPOUNDS— MIXTURES— VALENCE,  ETC.  17 

CuSOi -51120.  Likewise,  the  formula  of  gypsum,  or  hy- 
drated  calcium  sulphate,  may  be  written  CaS04 -21120. 
When  this  is  heated,  it  loses  three-fourths  of  its  water, 
and  the  resulting  plaster  of  Paris  has  the  formula 
(CaS04)2-H20. 

The  number  of  bonds  which  each  component  part  of 
a  compound  possesses  determines  its  formula.  Thus,  in 
sodium  chloride,  sodium  and  chlorine  each  have  one  bond, 
and  therefore  the  formula  is  NaCl.  In  sodium  sulphide, 
the  sulphur  atom  has  two  bonds,  and  therefore  requires 
two  sodium  atoms,  each  with  its  one  bond,  to  satisfy  it; 
consequently  the  formula  is  Na2S.  In  arsenious  oxide,  it 
requires  two  arsenic  atoms,  each  with  three  bonds  or  six 
together,  and  three  oxygen  atoms,  each  with  two  bonds, 
to  make  the  formula,  AS2O3,  in  which  the  total  bonds  of 
the  arsenic  atoms  shall  equal  the  total  bonds  of  the  oxy- 
gen atoms.  In  some  conditions,  arsenic  develops  five  bonds, 
and  consequently  the  formula  of  arsenic  oxide  is  AS2O5. 

19.  Criss-cross  Rule.  In  compounds  which  are  com- 
posed of  two  units,  the  formula  may  be  determined  by 
taking  as  many  atoms  or  parts  of  one  component  as  there 
are  bonds  of  the  other  component.  This  is  more  apparent, 
if,  first,  the  bonds  of  each  part  are  indicated.  Thus,  in 
determining  the  formula  of  aluminium  oxide,  write  the 
symbols  and  indicate  the  bonds  of  each,  k\"'0",  then, 
applying  the  ''  criss-cross "  rule,  the  formula  becomes 
AI2O3.  In  the  formula  for  copper  sulphide  the  bonds 
would  be  Cu"S",  and  the  formula,  CU2S2;  but  it  is  cus- 
tomary to  reduce  such  formulas  to  their  lowest  terms,  which 
in  this  case  will  be  CuS. 

In  formulas  having  more  than  two  components,  very 
frequently  two  or  more  of  the  elements  group  themselves 
together  and  act  as  a  unit.  Such  groups  do  not  generally 
separate  when  they  take  part  in  a  chemical  reaction.  They 
are  termed  radicals.  Thus,  in  the  formula  of  phosphoric 
acid,  H3PO4,  the  PO4  acts  as  a  radical,  and  in  the  formula 


18  CHEMISTRY  OF  FARM  PRACTICE 

for  ammonium  carbonate  (NH4)2C03,  the  NH4  and  the 
CO3  are  each  radicals.  Radicals  may  be  considered  as 
having  free  bonds,  the  same  as  elements.  In  H3PO4  the 
PO4  has  three  bonds.  This  is  indicated  by  the  fact 
that  it  requires  three  monovalent  hydrogen  atoms  to  sat- 
urate it. 

In  acids  the  portion  after  subtracting  the  acid  hydrogen 
is  a  radical,  and  its  bonds  are  indicated  by  the  number  of 
acid  hydrogens  subtracted,  m  salts  the  portion  transferred 
from  the  acid  from  which  it  was  derived  is  a  radical  with 
the  same  number  of  bonds  as  in  the  acid.  In  bases,  the 
hydroxyl,  OH,  is  a  radical,  each  hydroxyl  having  one  free 
bond. 

By  following  these  directions,  the  formulas  of  the  com- 
mon compounds  may  be  written,  provided  the  bonds  of 
the  elements  and  the  formulas  of  the  acids  are  in  mind. 
On  the  other  hand,  the  bonds  of  elements  and  radicals 
may  be  inferred  if  the  formulas  of  compounds  are  known. 

The  formula  of  the  salt,  calcium  silicate,  may  be  de- 
rived as  follows:  This  silicate  salt  is  related  to  silicic  acid. 
SiUcic  acid  has  the  formula  H4Si04.  Its  acid  radical  is 
Si04,  which  has  four  bonds,  as  shown  by  the  four  hydrogen 
atoms.  Calcium  is  a  bivalent  radical.  This  could  be 
inferred  if  a  formula  of  any  common  substance  containing 
calcium  is  known,  e.g.,  CaCl2  or  Ca(0H)2.  Chlorine,  we 
know,  has  one  bond,  and  applying  the  criss-cross  rule,  we 
have  Ca"Cl2',  therefore,  calcium  is  bivalent.  Now,  writing 
for  calcium  silicate,  CaSi04,  and  inserting  the  marks  for 
the  bonds,  Ca"(Si04)"",  and  applying  the  criss-cross  rule. 
Ca4 (8104)2,  and  reducing  to  its  lowest  terms,  we  have  the 
correct  formula  Ca2Si04. 

We  may  derive  the  formula  for  aluminium  sulphate  in 
a  similar  way.  A  sulphate  is  related  to  sulphuric  acid, 
H2SO4.  The  acid  radical  SO4  has  two  bonds,  because  of 
its  two  hydrogen  atoms.  Aluminium  has  three  bonds,  as 
indicated   by   the   formula  for  its  oxide,   Al2'"03".      So, 


COMPOUNDS— MIXTURES— VALENCE,  ETC.  19 

inserting  the   bonds,   we  have   A1'"(S04)",   and   applying 
the  rule,  the  correct  formula  would  be  Al2(S04)3. 

20.  Equations.  Chemical  reactions  are  expressed  by 
equations  which  show  in  a  condensed  form  the  kind  and 
the  quantities  both  of  the  substances  entering  into  the 
reaction  and  of  the  products  formed.  Equations  may  be 
placed  in  four  classes: 

(1)  Combination.  When  two  or  more  substances  unite 
to  form  a  new  combination,  as,  by  example, 

Fe+S  =  FeS. 

This  equation  is  read,  one  atom  of  iron  unites  with 
one  atom  of  sulphur  to  produce  one  molecule  of  iron  sul- 
phide. 

It  also  indicates  that  one  atomic  weight  of  iron,  56, 
is  uniting  with  one  atomic  weight  of  sulphur,  32,  and  pro- 
ducing a  molecular  weight  of  iron  sulphide,  88. 

H2+0  =  H20. 

This  may  be  translated,  one  molecule  of  hydrogen 
weighing  2,  unites  with  one  atom  of  oxygen  weighing  16, 
and  produces  one  molecule  of  water  weighing  18. 

(2)  Decomposition.  When  a  substance  is  separated  into 
two  or  more  substances,  the  analysis  may  be  expressed 
as  follows: 

H2C03  =  H20  +  C02. 

This  may  be  read,  one  molecule  of  carbonic  acid,  weight 
62,  is  decomposed  into  one  molecule  of  water,  weight  18, 
and  one  molecule  of  carbon  dioxide,  weight  44. 

Fe203  =  2Fe+30. 

One  molecule  of  ferric  oxide  yields  two  atoms  of  iron 
and  three  atoms  of  oxygen. 

It  is  known  that  oxygen  in  a  free  condition  exists  as 
molecules  of  two  atoms  each.     The  number  of  atoms  in 


20  CHEMISTRY  OF  FARM  PRACTICE 

a  molecule  of  metallic  iron  has  not  been  determined.  There- 
fore, by  doubling  the  equation  above,  it  may  be  so  written 
as  to  meet  these  conditions. 

2Fe203  =  4Fe+302. 

This  is  read,  two  molecules  of  ferric  oxide  will  produce 
four  atoms  of  iron  and  three  molecules  of  oxygen. 

(3)  Substitution.  Frequently  an  element  may  be  sub- 
stituted for  a  portion  of  a  compoimd,  provided  it  is  chem- 
ically equivalent  to  the  displaced  portion. 

Mg+2HC1  =  MgCl2+H2. 

One  atom  of  bivalent  magnesium  here  substitutes  for 
two  atoms  of  monovalent  hydrogen. 

The  formula  for  water,  H2O,  may  be  written  HOH, 
in  which  OH  is  a  radical.  Metals  such  as  sodium  react 
with  water  as  shown  by  the  substitution  equation. 

Na+HOH  =  H+NaOH. 

This  equation  doubled, 

2Na+2HOH  =  H2+2NaOH, 

would  be  read,  two  atoms  of  sodium  plus  two  molecules 
of  water  will  produce  one  molecule  of  hydrogen  and  two 
molecules  of  sodium  hydroxide. 

When  iron  is  exposed  to  steam  the  reaction  would  be 
expressed, 

Fe+3HOH  =  Fe(OH)3+3H, 
or  better, 

2Fe+6HOH  =  2Fe(OH)3+3H2. 

(4)  Double  Decomposition.  When  acids  or  bases  or 
salts  react  with  one  another,  there  is  a  simple  exchange 
between  the  parts  of  the  decomposing  substances.  This 
is  the  most  common  sort  of  chemical  equation. 


COMPOUNDS— MIXTURES— VALENCE,  ETC.  21 

In  writing  such  equations,  first  indicate  this  change. 
Thus,  in  the  case  of  the  reaction  between  nitric  acid  and 
copper  hydroxide, 

HN03+Cu(OH)  =  CuN03+HOH. 

Then  indicate  the  bonds  of  the  different  radicals  and  ele- 
ments 

H(N03)'+Cu"(OH)'  =  Cu"(N03)'+H"(OH)'. 

Next  correct  the  formulas  by  noting  the  bonds  and  em- 
ploying the  criss-cross  rule, 

HN03+Cu(OH)2  =  Cu(N03)2+HOH. 

Select  one  of  the  more  complicated  formulas,  such  as 
Cu(N03)2,  and  check  off  its  parts  to  see  if  an  equal  number 
of  such  parts  appear  on  the  other  side  of  the  equation. 
Note  that  it  has  two  (NO3)  radicals,  which,  to  balance  the 
equation,  must  appear  in  the  left-hand,  or  factor  side  of 
the  equation:  so  take  2HNO3.  Likewise  note  the  two  OH 
of  Cu(0H)2,  and  provide  for  their  appearance  on  the 
right  or  product  side  of  the  equation,  i.e.,  2H0H.  The 
equation  now  becomes, 

2HN03+Cu(OH)2  =  Cu(N03)2+2HOH. 

Finally,  check  off  each  element  or  radical  and  see  that  it 
appears  an  equal  number  of  times  on  each  side  of  the 
equation.     The  equation  then  balances  and  will  be  correct. 

In  a  similar  manner,  the  equation  expressing  the  reac- 
tion between  the  two  salts,  antimony  sulphide  and  sulphuric 
acid  may  be  balanced. 

SbS + H2SO4        =  SbS04 + H2S  (exchanging  radicals) , 
Sb'"S"+H2S04  =Sb"'(S04)"+H'S"  (indicating  bonds), 
Sb2S3+H2S04     =Sb2(S04)3+H2S  (correcting  formulas), 
Sb2S3+3H2S04  =  Sb2(S04)3+3H2S  (balancing  and  checking 
off). 


22  CHEMISTRY  OF  FARM  PRACTICE 

In  the  reaction  between  phosphoric  acid,  H3PO4,  and 
sodium  hydroxide,  NaOH,  if  there  were  present  enough  of 
the  base  to  replace  one  only  of  the  three  acid  hydrogens, 
we  could  represent  the  action  by  the  equation, 

I  NaOH+H3P04  =  NaH2P04+H20. 

£n  the  formula  of  the  sodium  dihydrogen  phosphate,  it 
will  be  noticed  that  the  three  bonds  of  the  acid  radical, 
PO4,  are  held  by  a  combination  of  three  bonds,  one  from 
the  sodium  atom  and  two  from  the  two  hydrogen  atoms. 

Should  there  be  sufficient  sodium  hydroxide  to  replace 
two  of  the  three  hydrogen  atoms  of  phosphoric  acid,  the 
trial  equation  would  be, 

NaOH+H3P04  =  Na2HP04+H20. 

It  will  be  seen  that  the  total  number  of  sodium,  oxygen, 
or  hydrogen  atoms  on  one  side  of  the  equation  does  not 
correspond  or  balance  the  atoms  of  these  elements  on  the 
other  side.  Starting  with  the  disodium  hydrogen  phos- 
phate, which  is  the  most  complicated  formula  of  the  equa- 
tion, its  two  sodium  atoms  require  two  sodium  atoms  in 
the  left-hand  or  factor  side  of  the  equation,  therefore,  we 
take  two  molecules  of  sodium  hydroxide.  The  equation 
then  will  be  balanced,  except  its  hydrogen  and  oxygen, 
which  may  be  made  equal  on  each  side  by  making  two 
molecules  of  water  on  the  product  side. 

11.  2NaOH-f  H3PO4  =  Na2HP04+2H20. 

When  there  is  excess  of  sodium  hydroxide,  Na3P04,  would 
be  formed  and  the  equation  would  be, 

III.  3NaOH + H3PO4  =  Na3P04 + 3H2O. 

Thus  we  find  three  different  reactions  represented  by  the 
three  equations  which  are  possible  when  sodium  hydroxide 
is  treated  with  phosphoric  acid. 


COMPOUNDS— MIXTURES— VALENCE,  ETC.  23 

Calcium  phosphate,  Ca3"(P04)2'",  is  used  as  a  source 
of  fertilizer.  As  it  is  very  insoluble  in  water,  in  order  to 
make  it  soluble  and  thereby  quickly  available  as  a  plant 
food,  it  is  treated  with  sulphuric  acid,  which  changes  the 
phosphate  into  a  more  soluble  form.  The  following  reac- 
tions may  take  place: 

I.  Ca3(P04)2+3H2S04  =  2H3P04+3CaS04, 
II.  Ca3(P04)2+2H2S04  =  CaH4(P04)2+2CaS04, 
III.    Ca3(P04)2+H2S04  =  2CaH(P04)+CaS04. 

These  equations  should  be  read  and  the  balancing  of  them 
checked. 


CHAPTER  III 

ACIDS— BASES— SALTS— ANHYDRIDES— DISSOCIATION- 
NOMENCLATURE 

21.  Groups  of  Elements.  The  chemical  elements  maj' 
be  roughly  divided  into  three  large  groups : 

(1)  Metal's.  These  are  base-forming  elements.  There 
are  somewhat  more  than  a  dozen  of  these  elements  that 
are  important. 

(2)  Non-metaTs.  These  are  acid-formers.  The  common 
acid-forming  elements  are  oxygen,  sulphur,  nitrogen,  carbon, 
silicon,  boron,  phosphorus,  fluorine,  chlorine,  bromine,  and 
iodine. 

(3)  Metalloids.  Between  the  two  groups  (1)  and  (2) 
are  a  few  intermediate  elements  which  act  either  as  acidic 
or  basic,  according  as  they  are  influenced  by  combination, 
on  the  one  hand  with  strong  basic  elements,  or  on  the 
other  hand  with  strong  acidic  elements.  These  border-line 
elements  thus  are  seen  to  be  rather  indifferent  in  their 
chemical  affinities.  The  common  metalloids  are  chromium, 
aluminium,  manganese,  arsenic,  antimony,  and  tin. 

22.  Classes  of  Compounds.  Most  of  the  compounds  of 
inorganic  chemistry  are  included  in  one  of  the  four  classes — 
acids,  bases,  salts,  and  anhydrides.  The  properties  and 
the  composition  of  each  of  these  classes  must  be  studied 
carefully  in  order  to  gain  a  working  knowledge  of  chemistry. 

23.  Acids.  The  most  important  acids  are  sulphuric, 
H2SO4;  hydrochloric,  HCl;  nitric,  HNO3;  phosphoric, 
H3PO4;  and  acetic,  HC2H3O2.  If  these  or  the  score  of 
other  commonly-occurring  acids  should  be  examined,  they 
all  will  be  found  to  have  the  following  characteristic  prop- 
erties : 

24 


ACIDS— BASES— SALTS— ANHYDRIDES,  ETC.  25 

(a)  They  are  sour  to  the  taste. 

(6)  They  have  the  power  of  turning  to  a  pink  color 
paper  that  has  been  stained  blue  by  an  organic  dye  com- 
monly called  litmus. 

(c)  When  in  water  solution,  they  attack  such  metals 
as  zinc  and  magnesium,  thereby  being  themselves  broken 
up  into  hydrogen  or  some  compound  of  hydrogen,  as  one 
of  the  decomposition  products.  Most  frequently,  this  action 
may  be  observed  by  the  bubbles  of  effervescing  gas  rising 
through  the  liquid  acid  solution. 

(d)  They  arc  soluble  in  water.  They  differ,  however, 
in  degree  of  solubility. 

(e)  They  contain  hydrogen,  which  is  easily  separated 
from  the  remainder  of  the  acid  when  it  acts  chemically 
upon  other  substances. 

(/)  Acids  react  with  bases,  thereby  neutralizing  or  de- 
strojdng  the  characteristic  properties  of  both  acid  and 
base. 

(g)  In  respect  to  their  composition,  acids  may  be  divided 
into  two  classes: 

(1)  The  Oxygen  Acids.     These  are  composed  of  hydrogen 

which  is  bound  by  means  of  oxygen  to  a  non-metallic  ele- 

m3nt  or  radical.     For  example,  hypochlorous  acid,  HCIO, 

may  be  considered  as  H — O — CI;  nitric  acid  as  H — O — NO2; 

H— 0\ 
sulphuric  acid  as  7SO2. 

H— 0/ 

(2)  Hydrogen  Acids.  These  do  not  contain  oxygen. 
The  formula  of  the  six  common  hydrogen  acids  are  HCl, 
HBr,  HF,  HI,  H2S,  HCN. 

24.  Bases.  Some  of  the  most  common  bases  are  sodium 
hydroxide,  NaOH;  potassium  hydroxide,  KOH;  ammo- 
nium hydroxide,  NH4OH;  calcium  hydroxide,  Ca(0H)2; 
barium  hydroxide,  Ba(0H)2.  Bases  have,  generally,  prop- 
erties the  opposite  of  those  exhibited  by  acids. 

(a)  Bases  that  are  soluljle  in  water  have  an  alkaline 
taste  and  feel  soapy  to  the  touch. 


26  CHEMISTRY  OP^  FARM  PRACTICE 

(6)  When  in  water  solution,  bases  turn  back  to  a  blue 
color  litmus  paper  that  has  been  made  pink  by  the  action 
of  an  acid. 

(c)  The  stronger  bases  attack  metals  such  as  aluminium 
and  zinc,  producing  thereby  water  as  one  of  the  products 
of  the  reaction. 

(d)  Generally  they  are  insoluble  in  water.  Those  enu- 
merated above  are  the  only  ones  that  will  dissolve  appre- 
ciably in  water.  The  three  first  mentioned  above  are 
very  soluble  and  are  called  the  alkalies. 

(e)  Bases  all  contain  the  radical,  hydroxyl,  OH,  the 
only  other  constituent  being  a  metal.  This  hydroxyl  is 
easily  separated  from  the  metal. 

(/)  Bases  react  easily  with  acids,  the  hydroxyl  of  the 
base  uniting  with  the  hydrogen  of  the  acid,  producing 
thereby  water  (0H+H  =  H20).  This  action  takes  away 
or  neutralizes  the  characteristic  properties  of  both  acids 
and  base. 

(g)  Bases  are  composed  of  a  metal  bound  by  means  of 
oxygen  to  hydrogen.  For  example:  silver  hydroxide, 
AgOH;  mercurous  hydroxide,  HgOH;  copper  hydroxide, 
Cu(0H)2;  iron  hydroxide,  Fe(0H)3. 

25.  Salts.  Salts  have  no  characteristic  properties  de- 
fining them  as  a  class.  They  may  l^e  best  described  by 
their   methods   of   production    and    by   their   composition. 

(a)  When  the  acid  hydrogen  of  an  acid  is  replaced  by 
a  metal,  the  resulting  compound  is  a  salt.  For  example: 
Replacing  the  two  hydrogens  of  sulphuric  acid,  H0SO4, 
by  the  bivalent  metal  zinc,  a  salt,  zinc  sulphate,  ZnS04, 
is  produced;  replacing  the  hydrogen  of  nitric  acid,  HNO3, 
by  the  univalent  metal  silver,  a  salt,  silver  nitrate,  AgNOs, 
is  produced. 

(6)  When  the  hydi-oxyl  of  a  base  is  replaced  by  a  non- 
metal  or  by  a  non-metallic  radical,  the  resulting  com- 
pound is  a  salt.  For  example:  When  the  hydroxyls  of 
the  base,   zinc  hydroxide,   Zn(0H)2,   are  replaced  by  the 


ACIDS— BASES— SALTS— ANHYDRIDES,  ETC.  27 

non-metallic  or  acid  radical,  SO4,  the  result  will  be  the 
salt,  zinc  sulphate,  ZnS04;  replacing  the  hydroxyl  of 
sodium  hydroxide  by  the  non-metallic  element,  chlorine, 
the  result  will  be  a  salt,  sodium  chloride,  NaCl. 

(c)  When  acids  and  bases  react  with  each  other,  water 
is  always  produced  by  the  union  of  the  hydrogen  of  the 
acid  with  the  hydroxyl  of  the  base,  H+0H  =  H20.  What 
is  left  of  the  acid  after  its  hydrogen  is  removed  is  the  acid 
radical.  For  example:  NO3  from  nitric  acid,  HNO3. 
What  is  left  of  the  base  after  its  hydroxyl  is  removed  is 
the  metal:  For  example,  K  from  the  base  potassium  hy- 
droxide, KOH.  These  remnants  will  unite  and  thereby 
form  a  salt;  K  and  NO3  produce  the  salt  potassium  nitrate, 
KNO3. 

There  are  four  classes  of  salts: 

(1)  Normal  Salts.  These  contain  only  the  metal  and 
the  acid  radical,  such  as  sodium  nitrate,  NaNOs,  or  potas- 
sium phosphate,  K3PO4.  They  may  be  regarded  as  the 
salts  in  which  all  the  hydrogen  of  the  acid  has  been  replaced 
by  a  metal. 

(2)  Acid  Salts.  In  these  one  or  more  of  the  hydrogens 
of  the  acid  from  which  the  salt  is  derived  has  been  re- 
tained. For  example:  sodium  hydrogen  sulphate,  NaHS04, 
potassium  hydrogen  phosphate,  KHSO4.  These  generally 
are  able  to  turn  blue  litmus  to  a  pink^color  on  account  of 
the  acid  hydrogen  left  in  them. 

(3)  Basic  Salts.  In  these,  some  of  the  hydroxyl  of 
the  base  from  which  the  salt  was  derived  has  been  retained. 
For  example,  basic  bismuth  nitrate,  Bi(0H)2N03.  This  is 
produced  by  substituting  the  acid  radical  NO3  for  one 
of  the  hj^droxides  of  the  base,  Bi(0H)3. 

(4)  Neutral  Salts.  These  salts,  when  in  water  solu- 
tion, do  not  change  color  in  either  blue  or  pink  litmus 
paper. 

26.  Anhydrides.  This  word  means  mthoiU  water.  An- 
hydrides may  be  considered  as  either  acids  or  bases  from 


28  CHEMISTRY  OF  FARM  PRACTICE 

which  water  has  been  subtracted.  They  are  quite  gen- 
erally oxides,  that  is,  compounds  in  which  oxygen  is  com- 
bined with  one  other  element.     There  are  two  classes: 

(1)  Acid  Anhydrides.  For  example:  Sulphuric  anhy- 
dride, SO3,  produced  by  subtracting  water,  H2O,  from 
sulphuric  acid,  H2SO4;  nitric  anhydride,  N2O5,  produced  by 
subtracting  water  from  two  molecules  of  nitric  acid,  HNO3. 

(2)  Basic  Anhydrides.  For  example:  Calcium  oxide, 
CaO,  produced  by  subtracting  water  from  the  base,  cal- 
cium hydroxide,  Ca(0H)2;  sodium  oxide,  Na20,  produced 
by  subtracting  water  from  two  molecules  of  the  base  NaOH. 

27.  Dissociation.  If  an  acid  or  a  base  or  a  salt  is  dis 
solved  in  water  and  a  current  of  electricity  is  passed  through 
the  solution,  it  will  be  found  that  the  compound  will  tend 
to  separate  into  two  parts,  one  of  which  will  accumulate 
at  the  +  electrode,  where  the  current  enters  the  solution, 
while  the  other  portion  will  condense  about  the  —  elec- 
trode, where  the  current  leaves  the  solution.  As  opposite 
kinds  of  electric  charges  attract  each  the  other,  the  portion 
attracted  to  the  +  electrode  is  called  the  electro-negative 
part  of  the  compound,  and  the  portion  attracted  towards 
the  —  electrode  is  called  the  electro-positive  portion  of  the 
compound.  These  portions,  because  they  move  through  the 
solution,  are  termed  ions.  In  the  case  of  acids  it  is  found 
that  the  replaceable  or  acid  hydrogen  of  the  acid  is  con- 
densed about  the  —  electrode,  and  is  therefore  electro- 
positive, while  the  remainder  of  the  acid,  the  acid  radical 
portion,  moves  toward  the  +  electrode  and  is  therefore 
electro-negative.     These   are  some  examples: 

HCl,   H(N03),    H(C2H302). 

When  salts  are  thus  electrolyzed,  the  metallic  part  of 
the  salt  is  found  to  be  electro-positive,  and  the  acid  radical 
part  is  electro-negative : 

+    -+-+-  +  -  + 

ZnCl2,  PbS,   Na3(P04),  Na(H2P04),  Nao(HP04). 


ACIDS— BASES— SALTS— ANHYDRIDES,  ETC.  29 

In  the  case  of  bases  the  metalUe  portion  is  electro- 
positive and  the  hydroxyl  is  electro-negative.  This  is 
indicated  in  the  following  formulas  of  bases: 

+       -       +      -         +      - 
Na(OH),   Ca(0H)2,   re(0H)3. 

There  are  reasons  for  believing  that  when  acids  or  bases 
or  salts  are  dissolved  in  water,  even  when  no  electric  cur- 
rent is  passing  through  the  solution,  the  compounds  to 
some  extent  break  up,  or,  as  it  is  termed,  dissociate  into 
ions  highly  charged  either  positively  or  negatively.  The 
ions  with  electro-negative  charges  are  acid-forming.  They 
are  either  the  non-metallic  elements  or  are  radicals  con- 
taining non-metals.  According  to  the  dissociation  theory, 
acids  are  electro-negative  elements  or  radicals  united  to 
hydrogen,  and  bases  are  electro-positive  elements  united 
to  hydroxyl  (OH),  and  salts  are  electro-positive  elements 
united  to  electro-negative  elements  or  radicals, 

28.  Nomenclature  of  Compounds.  Names  are  given 
to  most  chemical  compounds  according  to  a  few  simple 
rules. 

(1)  Nomenclature  of  Binary  Compounds,  (a)  Compounds 
composed  of  two  elements  have  names  ending  in  ide.  This 
affix  is  attached  to  the  abbreviated  name  of  the  non- 
metallic  part  of  the  compound.  Thus  oxygen  forms  oxides, 
as  calcium  oxide,  CaO;  sulphur  forms  sulphides,  as  lead 
sulphide,  PbS;  chlorine  forms  chlorides,  as  sodiiun  chloride, 
NaCl.  To  indicate  the  number  of  atoms  of  the  non- 
metalUc  element  in  the  compounds,  the  prefixes  mono  for 
one,  di,  for  two,  tri  for  three,  and  tetra  for  four,  are  used; 
thus  CO  is  carbon  monoxide;  SO2  is  sulphur  dioxide;  AsCla 
is  arsenious  trichloride;  CCI4  is  carbon  tetrachloride. 

(6)  In  case  two  compounds  are  made  by  the  same  two 
elements  entering  into  combination  in  varying  propor- 
tion, the  name  of  the  metallic  element  is  modified  by  the 
terminations  ous  or  ic.    Thus  HgCl  is  called  mercurows 


30  CHEMISTRY  OF  FARM  PRACTICE 

chloride,  and  HgCl2  is  called  mercuric  chloride.  The 
compound  in  which  there  is  the  larger  ratio  of  non-metallic 
component  assumes  the  termination  ic,  while  the  com- 
pound having  the  smaller  proportion  of  the  non-metallic 
component  has  the  termination  ous.  For  example:  FeO 
is  ferroMS  oxide;  Fe203  is  ferrfc  oxide;  SnS  is  stannous 
sulphide;  SnS2  is  stannic  sulphide. 

(2)  Nomenclature  of  Acids.  The  name  of  the  acid- 
forming  element  to  which  is  added  the  affix  ic  is  assigned 
to  the  most  common  acid  formed  by  that  element:  Thus 
sulphuric  acid,  H2SO4;  phosphoric  acid,  H3PO4;  chloric 
acid,  HCIO3.  When  the  elements  form  an  acid  which 
contains  a  larger  amount  of  oxygen,  the  prefix  per  is  used, 
as  persulphuric  acid,  H2S4O8.  In  case  the  element  forms 
an  acid  containing  less  oxygen  than  its  ic  acid,  the  termina- 
tion ous  is  used,  as  sulphurous  acid,  H2SO3.  An  acid  with 
still  less  oxygen  is  designated  by  the  prefix  hypo  as  well  as 
the  affix  ous;  as  H2SO2,  %posulphurows  acid. 

(3)  Nomenclature  of  Salts.  Names  of  those  salts  which 
contain  more  than  two  elements  are  determined  from  the 
names  of  the  acids  from  which  they  are  derived.  Here 
are  the  two  important  cases: 

The  names  of  salts  end  in  ate  which  are  derived  from  acids 
ending  in  ic. 

The  names  of  salts  end  in  ite  which  are  derived  from 
acids  ending  in  ous. 

Examples: 

Sodium  sulphate,  Na2S04,  formed  from  sulphuric  acid, 
H2SO4. 

Silver  nitrate,  AgN03,  formed  from  nitric  acid,  HNO3. 

Sodium  sulphite,  Na2S03,  formed  from  sulphurous  acid, 
H2SO3. 

Sodium  /i?/posulphite,  Na2S02,  formed  from  hyposul- 
phuroMs  acid,  H2SO2. 

The  following  illustrate  the  series  of  chlorine  acids 
and  the  salts  derived  from  them: 


ACIDS— BASES— SALTS— ANHYDRIDES,  ETC.  31 

HCIO4,  perchloric  acid:  KCIO4,  potassium  perchlorate. 

HCIO3,  chlorzc  acid:  KCIO3,  potassium  chlorate. 

HCIO2,  chloroi^  acid:  KCIO2,  potassium  chlorite. 

HCIO,  hypochlorous  acid:  KCIO,  potassium %pochlon<«. 

Salts  derived  from  the  hydrogen  acids,  such  as  HCl, 
HBr,  H2S,  contain  but  two  elements  and  follow  the  rule 
in  1  (a)  rather  than  that  of  3;  thus  CaCl2,  from  hydrochloric 
acid,  is  not  called  calcium  hydrochlorate,  but  is  termed 
calcium  chloride. 


CHAPTER  IV 

THE  ELEMENTS  NECESSARY  FOR  PLANT  GROWTH- 
OXYGEN— HYDROGEN— CARBON— NITROGEN— PHOS- 
PHORUS—SULPHUR— POTASSIUM— CALCIUM— MAGNE- 
SIUM— IRON 

29.  Oxygen.  Oxygen  is  the  most  abundant  of  the  ele- 
ments. Upon  it  the  life  of  plants  as  well  as  of  animals 
directly  depends.  The  greater  part  of  the  energy  mani- 
festing itself  in  the  motion  of  objects  about  us  is  the  result 
of  the  chemical  activity  of  oxygen.  Power  for  the  pur- 
poses of  commerce,  energy  which  drives  electric  and  steam 
cars,  and  the  heat  necessary  for  the  sustenance  of  life 
and  the  maintenance  of  a  temperature  which  makes  life 
possible  in  other  than  tropical  countries,  all  are  derived 
from  heat  produced  when  oxygen  combines  with  com- 
bustible substances. 

Occurrence.  In  a  free  condition  oxygen  exists  in  vast 
quantities  in  the  atmosphere,  of  which  it  is  nearly  21  per 
cent  by  volume.  In  combination  with  other  elements  it 
is  found  in  thousands  of  different  compounds.  Nearly 
nine-tenths  of  water  is  oxygen.  It  forms  nearly  one-half 
of  the  rocks  composing  the  crust  of  the  earth.  It  is  rather 
difficult  to  find,  in  any  of  the  common  objects  about  us, 
a  substance  that  is  not  combined  with  oxygen.  Other 
than  those  substances  that  have  been  artificially  produced 
by  man  and  those  that  like  carbon  in  coal  are  the  product 
of  vegetable  life,  almost  the  entire  earth  is  composed  of 
oxygen  compounds. 

Properties.  When  free,  oxygen  is  an  odorless  gas 
without  color  or  taste.  It  is  a  little  heavier  than  air  and 
is  soluble  in  water  at  ordinary  temperature  to  the  extent 

32 


ELEMENTS  NECESSARY  FOR  PLANT  GROWTH        33 

of  three  volumes  of  the  gas  to  one  hundred  volumes  of  the 
liquid.  Fish  and  other  marine  life  are  dependent  upon 
this  oxygen  dissolved  in  the  water.  With  very  few  excep- 
tions oxygen  forms  compounds  with  all  the  other  ele- 
ments; in  this  respect  no  other  element  can  compare  with 
oxygen. 

The  activity  of  oxygen  in  forming  chemical  combina- 
tion is  remarkably  increased  by  raising  its  temperature. 
Many  substances  that  resist  any  except  very  slow  oxidation, 


Fig.  6. — Preparation  of  oxygen  in  the  laboratory. 

when  heated  in  the  air,  will  unite  with  oxygen  so  rapidly 
that  they  suffer  combustion.  This  is  remarkably  apparent 
when  a  building  in  conflagration  is  entirely  consumed  in 
a  short  time.  Oxygen  is  absolutely  essential  in  the  build- 
ing up  of  plant  tissues.  The  carbohydrates,  the  proteids, 
and  the  fats,  the  constituents  of  plants  that  give  to  them 
their  value  as  foods,  are  composed  in  large  part  of  oxygen. 

In  the  process  of  decay  and  in  the  disposal  of  sewage, 
oxygen  plays  a  beneficial  role,  decomposing  germs  that, 
if  allowed  to  multiply,  would  produce  epidemic  diseases. 


34  CHEMISTRY  OF  FARM  PRACTICE 

Preparation.  Although  oxygen  exists  at  hand  in  enor- 
mous quantities  in  a  free  condition  in  the  air,  yet  it  is 
easier  to  obtain  it  by  decomposing  some  of  its  compounds 
than  to  try  to  separate  it  from  the  nitrogen  with  which 
it  is  mixed  in  the  atmosphere.  In  the  chemical  laboratory 
it  may  be  produced  by  heating  in  a  test-tube  a  Uttle  of  the 
white  salt,  potassium  chlorate  (KCIO3).  This  melts  at 
a  comparatively  low  temperature  (360°  C.)  and  soon  begins 
to  boil,  yielding  an  abundant  supply  of  oxygen.  This 
decomposition  takes  place  at  a  stiU  lower  temperature 
(200°  C.)  when  the  black  mineral,  pyrolusite  (manganese 
dioxide)  is  mixed  with  the  potassium  chlorate  in  the  pro- 
portion of  three  parts  of  the  chlorate  to  one  part  of  the 
pyrolusite.  The  method  of  producing  and  of  collecting 
the  gas  is  shown  in  Fig.  6. 

30.  Hydrogen.  The  element  hydrogen  is  a  colorless 
gas.  Very  little  is  found  in  a  free  condition,  although  a. 
small  amount,  estimated  as  one  part  in  thirty  thousand, 
exists  in  the  air.  It  is  not  so  active  chemically  as  oxygen, 
forming  compounds  with  comparatively  few  of  the  other 
elements. 

Occurrence.  Some  of  the  compounds  of  hydrogen  are 
of  great  importance.  The  principal  source  of  hydrogen  is 
water,  of  which  it  constitutes  about  11  per  cent.  It  is  an 
essential  ingredient  of  animal  and  plant  structure.  Organic 
substances,  such  as  starch,  sugar,  albumen,  and  fat;  bodies 
formed  from  organic  matter,  such  as  petroleum  oil,  bitu- 
minous coal,  and  coal  tar,  and  the  vast  number  of  hydro- 
carbons, such  as  marsh  gas,  and  acetylene,  and  the  alcohols, 
all  are  made  in  part  of  hydrogen.  All  acids  and  all  bases 
contain  hydrogen  as  an  essential  ingredient.  Ammonia 
and  its  compounds,  which  form  an  important  food  for 
plants,  contain  hydrogen. 

Preparation.  Hydrogen,  as  well  as  oxygen,  may  be 
obtained  by  the  electrolysis  resulting  when  an  electric 
current  is  passed  through  water.    In  order  that  the  elec- 


ELEMENTS  NECESSARY  FOB.  PLANT  GROWTH        35 


trie  current  may  pass  through,  the  water  is  first  mixed 
with  a  Httle  sulphuric  acid.  The  gases  are  most  easily 
collected  by  means  of  an  apparatus  shown  in  Fig.  7.  The 
volume  of  the  hydrogen  evolved  is  twice  that  of  the  oxygen. 
Properties.  Hydrogen  will  burn  in  air  with  a  blue 
flame,  yielding  a  quantity  of 
heat  greater  than  that  pro- 
duced by  the  combustion  of 
the  same  weight  of  any  other 
combustible.  A  quarter  of  a 
ton  of  hydrogen  when  burned 
will  furnish  as  much  heat  as 
can  be  obtained  from  a  ton 
of  coal.  For  this  reason  coal 
gas,  which  is  composed  of 
about  50  per  cent  of  hydrogen, 
is  an  economical  fuel  for  cook- 


Oxygen 


Hydrogen 


Fig.  7. — Electrolysis  of  water. 


mg  purposes. 

Hydrogen  is  the  Hghtest 
known  substance.  Air  is  nearly 
14^  times  as  heavy  as  hy- 
drogen gas,  hence  the  latter 
is  used  for  inflating  balloons  and  for  dirigibles.  Hydrogen 
is  a  product  of  the  decay  of  many  organic  bodies.  When 
burned  in  air,  it  unites  with  oxygen  and  produces  steam 
according  to  the  equation 

H2+0  =  H20. 

31.  Carbon.  Next  to  oxygen  carbon  enters  most 
abundantly  into  the  composition  of  plants.  It  is  a  very 
important  element,  although  not  nearly  so  v/idely  distrib- 
uted as  oxygen.  It  exists  in  the  air  in  the  form  of  the 
compound  carbon  dioxide  gas,  CO2,  constituting  nearly 
four  parts  in  ten  thousand  parts  of  air.  Carbon  exists 
in  the  soil  as  the  carbonates  of  certain  metallic  elements 
such  as  calcium  and  magnesium.     The  diamond  is  a  crys- 


36  CHEMISTRY  OF  FARM  PRACTICE 

tallized  form  of  carbon.  Most  of  anthracite,  bituminous 
coal,  and  charcoal  is  carbon.  Graphite  is  almost  pure 
carbon. 

The  three  compounds  of  carbon  that  interest  us  most 
from  an  agricultural  view-point  are  carbon  dioxide,  the 
carbonates,  and  the  carbohydrates.  The  soil  water  con- 
tains a  certain  amount  of  carbon  dioxide,  which  is  produced 
through  the  decay  of  organic  matter  in  the  earth.  The 
higher  the  per  cent  of  carbon  dioxide  in  the  water,  the 
greater  will  be  its  solvent  power.     Thus,  water  percolating 


OJPPER  EPIDERMIS  LOWER  EPIDERMIS  CROSS  SECTION 

Fig.  8. — Structure  of  a  leaf.     The  stomata  are  shown  in  the  lower 
epidermis  and  in  the  cross-section. 

through  the  soil  and  absorbing  carbon  dioxide  will  dissolve 
mineral  matter  and  become  hard  water. 

The  carbonates  are  compounds  of  carbon  dioxide  and 
a  basic  anhydride.  Thus,  CaO+C02  =  CaC03.  Carbon- 
ate of  lime,  CaCOa,  is  agriculturally  the  most  important  of 
the  carbonates.  The  carbohydrates  contain  carbon  and 
hydrogen  and  oxygen,  the  latter  two  being  in  the  pro- 
portion of  water,  H2O.  The  carbohydrates  are  formed 
in  plants  by  the  condensation  of  formic  aldehyde.  Formic 
aldehyde  is  formed  in  the  green  part  of  plants  in  the  presence 
of  sunlight,  by  the  union  of  carbon  dioxide,  which  enters 
through  the  stomata  or  breathing  pores  of  the  leaf  of  the 


ELEMENTS  NECESSARY  FOR  PLANT  GROWTH        37 

plant,  with  water.     During  this  process,  oxygen  is  given 
off  from  the  plant. 

32.   Nitrogen.     When    pure,    nitrogen    is    a    colorless. 


Fig    9. — Roots  of  red  clover  showing  nodules  by  which  nitrogen  is 
secured  for  the  plant. 


odorless,  tasteless  and  very  inactive  gas.  It  combines 
directly  with  but  few  elements,  although  indirectly  it  enters 
into  the  formation  of  a  large  number  of  compounds  possess- 


38  CHEMISTRY  OF  FARM  PRACTICEj 

ing  very  marked  properties.  Nitrogen,  in  the  free  state, 
forms  about  fom-'fifths  by  volume  of  the  atmosphere; 
it  exists  in  combination  with  other  elements  in  important 
compounds,  such  as  ammonium  hydroxide  (NH4OH),  one 
of  the  alkali  bases;  in  nitric  acid  (HNO3),  one  of  the  strongest 
acids;  and  in  the  ammonium  form  (NH4),  as  a  salt  of  many 
acids.  It  is  present  in  combination  in  animal  and  in  plant 
tissues.  Nitrogen  is  available  as  plant  or  animal  food 
only  when  it  enters  into  some  combination.  It  is  the  most 
expensive  and  at  the  same  time  the  most  elusive  element 
with  which  the  farmer  has  to  deal. 

While  four-fifths,  by  volume,  of  the  atmosphere  is 
nitrogen,  most  plants  are  powerless  to  extract  it  from 
the  air.  A  small  amount  of  ammonia  gas  is  formed  in 
the  atmosphere  by  electrical  discharges  and  washed  to 
the  earth  by  rain  water;  in  a  similar  way  some  of  the 
oxides  of  nitrogen  are  formed.  Certain  bacteria  that  exist 
on  decaying  organic  matter  have  the  power  of  "  fixing  " 
atmospheric  nitrogen  in  such  combination  that  it  will 
become  available  to  the  plants.  A  large  amount  of  atmos- 
pheric nitrogen  is  "  fixed "  by  means  of  bacteria  that 
exist  in  so-called  symbiotic  union  with  leguminous  plants. 
These  bacteria  form  nodules  on  the  roots  of  the  plants 
which  they  infest,  as  shown  in  Fig.  9,  the  plants  furnishing 
food  for  the  bacteria,  while  the  bacteria  take  nitrogen 
from  the  atmosphere  and  convert  it  into  such  a  form  that 
the  plants  can  use  it  for  the  elaboration  of  their  tissues. 
Peas,  beans,  vetches,  clovers,  alfalfa,  peanuts,  and  beggar- 
weeds  are  examples  of  legumes. 

33.  Phosphorus.  Phosphorus  is  very  easily  oxidized, 
and,  therefore,  exists  in  nature  in  compounds  only.  It 
is  quite  widely  distributed  in  combination  with  oxygen 
and  calcium,  as  phosphate  rock,  which  is  largely  calcium 
phosphate  Ca3(P04)2.  Phosphorus  is  often  deficient  in 
soils,  and,  as  it  is  used  rather  plentifully  for  the  develop- 
ment of  both  plants  and  animals,  it  is  very  often  necessary 


ELEMENTS  NECESSARY  FOR  PLANT  GROWTH        39 

to  make  applications  of  it  in  a  commercial  form.  It  is  a 
necessary  constituent  of  the  bones  of  animals,  which  are 
composed  in  part  of  calcium  phosphate.  Phosphorus  has 
an  important  part  to  play  in  the  formation  of  the  seeds  of 
plants  and  in  hastening  their  maturity.  When  freshly 
prepared  and  kept  in  the  dark,  the  element  phosphorus  is 
an  almost  colorless  or  slightly  yellow,  waxlike  solid.  It 
has  a  remarkably  low  kindling  temperature,  and  therefore  it 
is  a  very  inflammable  substance,  and  must  be  kept  under 
water.  Phosphorus  appears  luminous  in  the  dark,  due  to 
its  slow  oxidation  to  phosphorous  trioxide  (P2O3)  when 
in  contact  with  moist  air.  Phosphorus  fumes  are  very 
poisonous.  When  yellow  phosphorus  is  heated  to  240°-250'' 
Centigrade,  it  is  changed  to  the  red  or  amorphous  form, 
which  has  a  much  higher  kindling  temperature  than  the 
yellow  form.  When  heated  to  260°  C,  it  is  again  changed 
to  the  yellow  form. 

34.  Sulphur.  Sulphur  occurs  as  yellow  crystals,  and 
also  as  opaque  crystalline  masses.  It  is  found  in  nature 
in  the  free  state,  most  frequently  in  volcanic  regions.  Com- 
pounds of  sulphur  with  metals  are  known  as  sulphides; 
and  when  these  compounds  are  more  completely  oxi- 
diAed,  they  become  sulphates.  Compounds  of  sulphur  are 
found  widely  distributed  in  both  plants  and  animals. 
Small  amounts  of  it  occur  in  hair  and  in  wool,  while  about 
1  per  cent  of  it  is  present  in  the  albuminous  substances 
which  are  present  to  a  large  extent  in  both  plants  and 
animals.  Sulphur  is  mined  in  large  quantities  in  Louisiana, 
where  the  supply  of  the  United  States  is  produced.  It 
is  also  produced  in  Sicily  and  Japan.  Most  of  our  soils 
contain  sufficient  sulphur  for  plant  growth. 

35.  Potassium.  Potassium  is  rather  abundant  in  nature, 
and  especially  so  in  soils  that  result  from  the  decompo- 
sition of  igneous  rock.  The  minerals  feldspar  and  mica 
contain  potassium  in  large  amounts.  Granite  rock  con- 
tains over  3  per  cent  of  potassium.     Sea  water  contains 


40 


CHEMISTRY  OF  FARM  PRACTICE 


J3 


-B 


oj  6 
.£  O 
S  ^ 

r  ^ 

2-  5 

CO  c 
=3  .2 


3 


? 


ELEMENTS  NECESSARY  FOR  PLANT  GROWTH        41 

some  potassium  in  the  form  of  sulphates  and  chlorides. 
Potassium  chloride  occurs  in  deposits  in  the  vicinity  of 


Stassfurt,  Germany,  where  it  is  mined  in  large  quantities. 
Some  seaweeds  contain  a  small  percentage  of  potassium; 


42  CHEMISTRY  OF  FARM  PRACTICE 

wood  ashes  contain  potash.     Potassium  has  a  tendency  to 
lengthen  the  growing  season  of  some  crops. 

36.  Calcium.  Compounds  of  calcium  are  widely  dis- 
tributed, but  the  element  does  not  occur  free  in  nature; 
it  may  be  prepared  by  electrolysis.  The  most  abundant 
compound  of  calcium  is  the  carbonate.  Calcium  carbonate 
or  "  ground  limestone  rock "  (CaCOs)  is  of  much  agri- 
cultural importance,  due  to  the  fact  that  it  corrects  acidity 
in  the  soil.  Calcium  carbonate  is  a  compound  that  is 
quite  readily  decomposed  by  other  acids.  Even  the  dilute 
acetic  acid  contained  in  vinegar  will  replace  the  carbonic 
acid  of  the  calcium  acetate. 

No  plant  growth  can  take  place  without  the  presence 
of  calcium.  It  has  been  shown  that  even  the  rather  insol- 
uble acid  silicate  of  calcium  may  serve  to  furnish  calcium 
to  the  plant.  All  normal  soils  have  a  supply  of  calcium 
compounds  sufficient  to  furnish  the  calcium  necessary  for 
plant  growth;  but  many  soils  are  acid  and,  therefore,  are 
benefited  by  applications  of  ground  limestone  to  correct 
the  acidity.     These  uses  will  be  taken  up  later. 

37.  Magnesium.  Magnesium  ranks  a  little  below  cal- 
cium in  its  abundance  in  nature.  It,  too,  never  occurs 
in  the  free  state  in  nature.  Its  compounds  are  quite  abun- 
dant in  the  earth's  crust,  in  rocks,  in  sea  water,  and  in 
mineral  water.  It  is  also  widely  distributed  in  both  animal 
and  vegetable  life.  It  exists  in  nature  largely  in  the  car- 
bonate form,  having  the  power  to  correct  soil  acidity, 
and  being  even  more  effective  for  this  purpose  per  unit 
of  weight  than  is  calcium  carbonate.  If,  however,  mag- 
nesium is  present  in  the  soil  in  excess  of  about  l^^  per  cent, 
it  produces  undesirable  effects  on  vegetation. 

38.  Iron.  Compounds  of  iron  are  widely  distributed 
in  nature  in  the  form  of  brown  or  yellow  oxides  giving 
characteristic  color  to  soils  and  as  carbonate.  These  com- 
pounds form  valuable  deposits  of  iron  ore.  Iron  sulphide 
in  the  form  of  pyrites  or  "  fool's  gold  "  is  frequently  foimd 


ELEMENTS  NECESSARY  FOR  PLANT  GROWTH        43 

in  coal-bearing  strata  and  in  other  rocks.     The  hydrated 
oxide  is  iron  rust 

39.  Summary.  Of  the  ten  elements  necessary  for  plant 
growth,  three — carbon,  hydrogen,  and  oxygen — are  exclu- 
sively derived  from  the  atmosphere;  one — nitrogen — 
partly  from  the  atmosphere  and  partly  from  the  soil; 
and  six — phosphorus,  potassium,  sulphur,  calcium,  mag- 
nesium, and  iron — are  derived  exclusively  from  the  soil. 
From  the  standpoint  of  plant  requirements  only  three  are 
often  deficient  in  soils — phosphorus,  nitrogen,  and  potas- 
sium, and  in  many  soils  only  one  or  two  elements  are  de- 
j&cient.  The  condition  of  the  soil  often  warrants  applica- 
tion of  lime  in  some  form. 


CHAPTER  V 

WATER— SOLVENT  ACTION  OF  WATER— DRINKING  WA- 
TER—SPRINGS—SHALLOW WELLS— DEEP  WELLS- 
TEMPORARY  HARDNESS— PERMANENT  HARDNESS- 
HOUSEHOLD   WATER 

40.  Properties  of  Water.  The  two  gaseous  elements, 
hydrogen  and  oxygen,  have  a  strong  chemical  attraction 
each  for  the  other.  They  unite  whenever  possible  in  the 
proportions  of  two  volumes  of  hydrogen  to  one  volume 
of  oxygen,  and,  by  weight,  in  the  proportion  of  one  unit 
of  hydrogen  to  eight  units  of  oxygen,  to  form  water,  which 
is  one  of  the  most  stable  of  compounds. 

Water  is  possessed  of  remarkable  physical  and  chemical 
properties.  In  common  with  most  liquids,  its  volume 
changes  with  heating  and  cooling.  When  water  is  cooled, 
Hs  maximum  density  is  attained  at  the  temperature  of 
4°  Centigrade.  This  temperature  is  still  4°  above  the 
freezing  temperature  of  water.  At  a  lower  temperature 
than  4°,  water  again  expands,  and  at  zero,  when  it  freezes, 
it  again  expands  suddenly.  This  latter  expansion  accounts 
for  the  disintegrating  effects  of  freezing,  the  force  being 
so  powerful  that  it  will  split  large  rocks,  and  it  also  accounts 
for  the  fact  that  ice  will  float.  This  remarkable  abnormal 
expansion  of  water,  when  the  temperature  falls  from  4° 
C.  to  0°  C,  results  in  the  formation  of  ice  at  the  surface 
of  a  cooing  body  rather  than  throughout  its  mass.  When, 
by  the  radiation  of  heat  into  the  air,  the  temperature  at 
the  surface  of  a  body  of  water  is  cooled  to  4°  C,  at  which 
temperature  it  is  densest,  the  cooled  surface  layers  will 
continue  to  sink  till  the  entire  mass  has  reached  the  tem- 
perature of  4°  C.     Should  the  water  grow  still  cooler,  by 

44 


WATER— SOLVENT  ACTION  OF  WATER,  ETC. 


45 


exposure  to  the  cold  air  above  it,  it  will  now  remain  at 
the  surface  supported  by  the  heavier,  though  warmer, 
water  beneath,  and,  finally,  when  the  surface  water  lowers 


to  zero,  it  will  freeze.  Ice,  being  a  solid  lighter  than  water, 
will  float  upon  it  and  being  a  poor  conductor  of  heat  will 
prevent  furfher  radiation  from  the  water  and  prevent  its 
freezing  more  than  to  a  limited  extent.  Were  it  not  for 
this  rather  miraculous  provision  of  nature,  the  lakes  and 


46  CHEMISTRY  OF  FARM  PRACTICE 

rivers,  even  in  temperate  zones,  would  freeze  from  bottom 
to  top  into  masses  of  ice  which  no  smnmer  smi  would  have 
power  to  melt.  Under  these  conditions  the  circulation  of 
water  would  be  prevented  and  our  latitudes  would  be  well- 
nigh  uninhabitable. 

When  water  under  atmospheric  pressure  is  heated  to 
a  temperature  of  100°  Centigrade,  or  212°  Fahrenheit, 
it  assumes  the  gaseous  form,  and  is  known  as  steam. 

41.  Solvent  Action  of  Water.  Water  is  the  most  widely 
distributed,  and  also  the  most  important  of  solvents.  It 
not  only  dissolves  plant  food,  but  also  serves  as  a  medium 
for  its  transportation  from  the  soil  to  the  plants.  All  of 
the  plant  food  that  is  derived  from  the  soil  is  taken  up 
from  solution;  hence  the  solubility  of  the  materials  deter- 
mines their  availability  as  plant  food. 

Water  charged  with  carbonic  acid  gas  is  the  most  im- 
portant natural  solvent.  In  the  decay  of  organic  matter 
in  the  soil  a  great  deal  of  carbonic  acid  and  some  nitric 
acid  are  liberated.  This  is  one  reason  why  it  is  desirable 
to  incorporate  a  large  amount  of  organic  matter  in  soil. 
The  nitric  acid  formed  during  the  process  of  nitrification 
is  a  stronger  solvent  than  carbon  dioxide;  but  the  quantity 
formed  is  comparatively  small,  hence  the  influence  of 
the  carbon  dioxide  as  a  solvent  in  the  soil  is  believed  to 
be  greater  than  that  of  nitric  acid.  The  nitric  acid  imme- 
diately reacts  with  the  basic  elements  in  the  soils,  such  as 
calcium,  sodium,  potassium,  magnesium,  and  ammonium, 
producing  metallic  nitrates,  all  of  which  are  soluble.  In 
this  way,  the  plant  may  be  furnished  not  only  with  nitrogen, 
but  with  potassium  or  calcium  as  well.  Phosphoric  acid 
and  monocalcium  phosphate  are  both  soluble  in  pure 
water.  Dicalcium  phosphate,  when  present  in  soil,  is 
insoluble  in  water,  but  it  may  be  dissolved  by  treating 
it  with  neutral  ammonium  citrate  of  a  specific  gravity  of 
1.09.  Tricalcium  phosphate  is  insoluble  in  water;  but  it 
is  soluble  to  some  extent  in  the  soil  moisture  when  the 


WATER— SOLVENT  ACTION  OF  WATER,  ETC.  47 

soil  is  well  supplied  with  decaying  organic  matter.  It  is 
probable  that  the  carbonic  acid  in  the  soil  solution  is  the 
most  effective  means  for  dissolving  tricalcium  phosphate, 
thus  making  it  available  as  a  plant  food. 

Table  II  shows  the  difference  between  the  solvent  action 


Fig.  13. — The  shallow  barnyard  well,  with  privy  vault  and  manure 
heaps  near  by.  The  water  is  likely  to  receive  fluid  from  these 
any  time.  (From  Smith's  "  Sewage  Disposal  on  the  Farm," 
Farmers'  Bulletin,  No.  43,  U.  S.  Department  of  Agriculture.) 


of  water  charged  with  carbon  dioxide  and  of  distilled 
water.  The  marked  increase  in  the  solvent  power  of 
water  when  carbonated  is  clearly  indicated. 

During  the  process  of  decomposition  of  organic  matter, 
the  nitrogen  is  changed  in  form.  The  organic  compounds 
of  nitrogen  are  changed  by  the  ammonifying  bacteria  into 


48 


CHEMISTRY  OF  FARM  PRACTICE 


TABLE  II.— THE  SOLUBILITY  OF  CERTAIN  MINERALS  IN 
DISTILLED  WATER  AND  IN  CARBONATED  WATER 


Name  of 
Mineral. 

Composition. 

Parts  per 

Million  Soluble 

in  Distilled 

Water. 

Parts  per 

Million  Soluble 

in  Carbonated 

Water. 

Calcite 

CaCOs 

34 

980 

Dolomite. .  .  . 

CaCOsMgCOs 

25 

325 

Apatite 

Ca3(P04)2,CaCl2CaF2 

3 

10 

Gypsum 

CaS04-2H20 

2390 

4600 

Feldspar.  .  .  . 

KAlSisOs 

20 

45 

Mica 

HsKAUlSiOOs 

5 

8 

Hematite. .  .  . 

FesO,, 

2 

15 

Quartz 

Si02 

1 

3 

ammoniacal  compounds.  These  compounds  are  oxidized 
by  the  activities  of  another  group  of  bacteria  into  nitrous 
compounds,  which  are  further  oxidized  by  other  bacteria 
into  nitric  compounds.  The  nitric  acid  thus  produced 
forms,  with  the  basic  elements  of  the  soil,  soluble  nitrate. 
Examples  of  these  have  already  been  mentioned.  It  should 
be  remembered  that  all  nitrates  are  soluble  in  water.  The 
formation  of  nitric  acid  and  its  subsequent  conversion  of 
bases,  formerly  in  insoluble  compounds,  into  nitrates,  which 
are  soluble  in  water,  and  the  increased  solvent  power  of 
the  soil  water  through  carbonation,  are  examples  of  the 
natural  solvents  and  their  action.  There  are  a  number  of 
organic  acids  both  in  the  soil  and  in  animal  manures  that 
have  solvent  powers;  but  the  study  of  them  requires  a 
large  mass  of  data  which  is  as  yet  incomplete.  It  is  suf- 
ficient to  say  that  they  exert  marked  activities  in  making 
available  food  for  plants. 

42.  Factors  Influencing  Availability  of  Plant  Food. 
Nature  provides  that  the  more  the  soil  is  worked,  the 
more  responsive  it  becomes  and  the  more  plant  food  be- 
comes available.  There  are  many  factors  influencing  the 
availability  of  the  plant  food  of  the  soil.    We  may  mention 


WATER— SOLVENT  ACTION  OF  WATER,  ETC.         49 

warmth,  moisture,  decaying  organic  matter,  cultivation, 
aeration,  and  freezing  as  the  most  important  ones.  An 
abundant  supply  of  organic  matter  in  a  soil,  its  proper 
cultivation  to  allow  an  abundant  circulation  of  air,  an 
abundant  supply  of  moisture,  avoiding  an  excess,  and 
warm  weather  are  the  conditions  best  suited  for  nitrifi- 
cation.    The  effects  of  frost  and  winds  are  mainly  physical, 


Shallow 
Dug  Well 


Deep 
Bored  Well 


Fig.  14. — Driven  and  dug  wells  showing  the  relative  danger  of  drain- 
age contamination.     (Farmers'  Bulletin  549,  U.  S.  Dept.  Agr.) 


and  result  in  more  finely  divided  soil  particles,  affording 
more  surface  area  for  the  activities  of  the  natural  solvents. 

43.  Drinking  Water.  Impure  water  transmits  many 
diseases,  among  which  may  be  mentioned  typhoid  fever, 
dysentery,  other  diarrhoeal  affections,  cholera,  cholera  in- 
fantum, animal  parasitic  diseases,  enteric  fever,  tuber- 
culosis, and  scarlet  fever.  Typhoid  fever  may  also  be 
spread  by  milk,  raw  fruit,  shell  fish,  or  flies.     Scarlet  fever 


50  CHEMISTRY  OF  FARM  PRACTICE 

is  more  often  spread  by  milk  than  by  water;  and  cholera, 
dysentery,  and  cholera  infantum  are  carried  by  milk  to 
some  extent.  Enteric  fever  is  carried  by  flies.  Each  of 
the  above-mentioned  diseases  is  spread  by  as  pecific  organ- 
ism, and  this  organism  must  first  get  into  the  water  for 
the  water  to  become  a  carrier  of  the  disease. 

It  has  been  estimated  that  approximately  one-third  of 
the  water  that  falls  runs  off  on  the  surface  of  the  ground 
into  streams.  This  water  is  termed  the  run-off.  Two- 
thirds  sinks  into  the  soil,  and  of  this,  approximately  one- 
half,  or  one-third  of  the  total  water,  is  lost  by  evaporation. 
This  is  termed  the  fly-off.  The  remainder,  approximately 
one-third  of  the  total  rainfall,  finds  its  way  out  in  springs 
or  through  subterranean  passages.  This  is  termed  the 
cut-off.  The  proportion  of  the  run-off,  fly-off  and  cut-off 
will  vary  with  differing  conditions,  but  the  above  esti- 
mate is  generally  approximately  true.  The  cut-off  is  the 
water  that  interests  us  from  the  standpoint  of  sanitary 
water  for  rural  homes. 

Farm  homes  are  usually  supplied  with  water  from  one 
of  three  sources:  springs,  shallow  wells,  or  deep  wells, 

(a)  Spring  water  is  contaminated,  and  may  be  infected, 
by  coming  in  contact  with  filth  of  any  kind;  for  this  reason 
the  water-shed  of  the  spring  should  not  have  on  it,  draining 
toward  the  springs,  any  barnyards,  pigsties,  privies,  slaughter 
houses,  or  graveyards.  The  spring  should  be  well  ditched 
around,  so  as  to  prevent  its  being  overflowed,  contaminated, 
and  possibly  infected.  It  is  generally  believed  that  the 
flowing  of  water  through  the  soil  purifies  it,  but  this  de- 
pends upon  the  character  of  the  ground  through  which 
it  flows.  Under  certain  conditions  (from  a  pathogenic 
standpoint)  old  water  may  be  better  than  fresh  water, 
because  the  germs  have  had  time  to  die. 

(b)  Shallow  wells  have  been  used  as  a  source  of  water- 
supply  since  Biblical  times.  They  are  likely  to  become 
infected  through  seepage  and  incomplete  filtration.     The 


WATER— SOLVENT  ACTION  OF  WATER,  ETC. 


51 


open  well  and  the  chain  and  bucket  should  be  discarded 
and  a  pump  with  a  closely  fitting  well  cover  which  does 
not  leak,  should  be  installed.  Arrangements  should  be 
made  for  the  removal  of  waste  water  and  to  prevent  the 
seepage  into  the  well  of  surface  water.  This  can  be  accom- 
plished, preferably,  by  the  use  of  cement,  or  a  brick  and 
mortar  structure  may  be  employed.  In  both  cases  the 
foundation  should  be  laid  well  below  the  surface  of  the 
ground,  as  in  Fig.  15,  and  upon  this  foundation  the  well 
cover  should  be  placed.  The  well  which  is  to  supply  the 
family  with  drinking  water  should  not  be  located  in  the 


ZZZZ22Z2ZZZZZ 


Fig.   15. — Proposed  method  of  protection  of  dug  wells. 
Bulletin  549,  U.  S.  Dept.  Agr.) 


(Farmers' 


barnyard  or  near  any  of  the  sources  of  possible  infection 
already  mentioned  in  connection  with  spring  water.  No 
drains  or  sewer  pipes  should  run  near  the  well  for  fear  of 
pollution,  contamination,  or  possible  infection  with  disease 
organisms. 

(c)  Deep  Wells.  Where  practicable,  artesian  wells,  Fig. 
16,  furnish  our  best  source  of  water-supply.  These  wells 
may  vary  in  depth  from  one  hundred  to  twenty-five  hundred 
feet.  Where  a  flowing  well  can  be  obtained  it  will  usually 
prove  to  be  the  best  and  most  economical  water-supply. 

After  having  seen  to  it  that  the  drinking  water-supply  is 
as  free  as  possible  from  infection,  the  factors  that  make  for 


52 


CHEMISTRY  OF  FARM  PRACTICE 


attractiveness  of  the  water  may  be  considered.  These  are 
taste,  odor,  color,  turbidity,  and  sediment.  The  desirabihty 
of  a  good  source  and  supply  of  water  cannot  be  urged 
too  strongly  on  the  rural  householder.  It  is  an  economic 
proposition,  saving  large  sums  in  expense  incident  to  sick- 
ness, and  even  more  through  increased  efficiency.  No  man 
can  work  to  best  advantage  when  handicapped  by  poor 


Fig.   16. — Flowing  well  near  Conway.  S.  C.     (Photo  by  Prof.  C.  E. 

Chambliss.) 


health,  which  in  many, cases  is  the  direct  result  of  a  poor 
water-supply. 

44.  Hardness  in  Water.  Hardness  in  water  is  caused 
by  the  presence  of  metallic  salts,  usually  those  of  calcium 
or  magnesium,  dissolved  in  the  water.  When  soap  is 
added  to  such  waters,  the  fatty  acid  radicals  of  the  soap 
combine  with  the  calcium  and  magnesium  and  produce 
an  insoluble  curdy  precipitate.  Until  all  of  these  calcium 
and  magnesium  salts  are  thus  precipitated,  no  lather  can 


WATER— SOLVENT  ACTION  OF  WATER,  ETC.  53 

be  obtained  with  the  soap  and  it  is  useless  as  a  cleansing 
agent.  Hardness  in  water  is  consequently  easily  determined 
by  adding  a  standard  soap  solution  to  the  water,  which 
will  produce  a  greasy  precipitate  with  the  calcium  and 
magnesium  salts  in  the  water.  Not  till  these  salts  are 
all  precipitated  can  a  permanent  lather  be  formed  on  the 
surface  of  the  water.  The  quantity  of  the  soap  solution 
needed  to  produce  the  lather  will,  therefore,  measure  the 
hardness  of  the  water. 

Hardness  may  be  classified  as  temporary  hardness  and 
permanent  hardness.  Temporary  hardness  is  usually  caused 
by  the  presence  of  dissolved  bicarbonates  of  calcium  and 
magnesium.  Permanent  hardness  is  usually  due  to  the 
chlorides  and  sulphates  of  these  elements.  Calcium  and 
magnesium  carbonates  are  insoluble,  but  if  carbon  dioxide 
is  present  in  the  water,  they  dissolve  to  some  extent,  forming 
the  bicarbonates.  Water  having  much  hardness  is  objec- 
tionable for  drinking  purposes.  For  bathing  and  laundry 
purposes,  it  is  expensive  on  account  of  the  large  amount 
of  soap  incident  to  its  use. 

Table  III  shows  the  relative  efficiency  of  a  number 
of  soaps  for  the  purpose  of  softening  water  as  given  by 
Whipple : 

According  to  Alexander  Smith,  with  water  containing 
35  grains  of  hardness  per  gallon  (60  parts  per  100,000), 
6  pounds  of  soap  are  wasted  per  100  gallons  of  water  before 
the  part  of  the  soap  that  is  to  do  the  work  of  cleansing 
begins  to  dissolve. 

When  we  consider  that  for  each  one  part  per  million 
of  hardness  it  requires  ten  dollars'  worth  of  soap  to  soften 
one  million  gallons  of  water,  it  emphasizes  the  expense 
in  the  use  of  hard  water  as  a  detergent. 

Temporary  hardness  may  be  removed : 

(1)  By  heating  the  water  to  boiling,  so  as  to  expel 
carbon  dioxide,  in  this  way  converting  the  soluble  bicar- 
bonate into  an  insoluble  carbonate; 


54  CHEMISTRY  OF  F.\RM  PRACTICE 

TABLE  III.— EFFICIENCY  OF  SOAPS  IN  SOFTENING  WATER 


-a  u 
e  o 

So 

Number  of  Gallons  of 

Water  Softened  by  C 

NE  Pound  of 

03  ^ 

5g 
|0 

I 

o 

u 

■a 

a 

OS 

1.1 

o'o  S 
3  ol"3 

0  si  . 
1,  O  t, 

PJ 

ci 
O 

•a  c3 
a  o 
3a2 

O 

m 
>> 

u 

o 

a 

3 
C3 
.-1 

^  P. 

¥ 

6 

"o 

0. 
C8 

< 

a 
o 

3 

Q 

T3 

"o 

a 

oi 

a; 

o 

m 

-a 
a 

X 

°  d 

11 

a-S§ 

o  aM 

» 

^1 

^ 

M 

" 

pq 

02 

m 

O 

P^ 

flH 

O 

< 

20 

2.1 

1.11 

409 

196 

138 

102 

143 

165 

167 

187 

225 

167 

25 

2.4 

1.27 

358 

174 

121 

90 

125 

145 

147 

164 

206 

147 

40 

3.6 

1.91 

238 

115 

80 

59 

83 

96 

98 

109 

137 

97 

50 

4.3 

2.28 

200 

96 

67 

50 

70 

81 

82 

92 

115 

82 

75 

6.1 

3.24 

140 

67 

47 

35 

49 

57 

58 

64 

80 

57 

80 

6.4 

3.49 

140 

70 

44 

33 

45 

52 

53 

60 

75 

54 

100 

7.8 

4.13 

110 

53 

37 

27 

38 

44 

45 

50 

63 

45 

125 

9.5 

5.04 

90 

43 

30 

25 

31 

36 

37 

41 

52 

37 

150 

11.1 

5.89 

77 

37 

26 

19 

27 

31 

32 

35 

44 

31 

175 

12.7 

6.74 

67 

32 

23 

17 

23 

27 

28 

31 

38 

27 

200 

14.3 

7.59 

60 

29 

20 

15 

21 

24 

25 

27 

34 

24 

(2)  By  treating  the  water  with  lye,  sodium  hydroxide, 
CaH2(C03)2+2NaOH  =  CaC03+Na2C03+2H20; 

(3)  By  treating  with  milk  of  lime, 

CaH2(C03)2+Ca(OH)2  =  2CaC03+2H20. 

Permanent  hardness  is  removed  by  treating  the  water 
with  sodium  carbonate.  The  following  equation  may  repre- 
sent the  reaction: 

CaS04+Na2C03  =  CaC03+Na2S04. 

The  calcium  carbonate  in  all  these  cases,  being  insoluble, 
will  be  precipitated  from  the  water,  leaving  in  the  water 
sodium  salts,  which  are  not  particularly  harmful. 

Magnesium  and  iron  salts  react  similarly  to  the  cal- 


WATER— SOLVENT  ACTION  OF  WATER,  ETC. 


55 


cium  salts,  though  the  iron  precipitates  as  the  hydroxide 
when  sodium  carbonate  is  the  precipitant.  Iron  is  objec- 
tionable in  laundry  work.  Sodium  carbonate  is  objection- 
able in  water  used  in  locomotive  boilers,  because  it  induces 
foaming;  it  is  also  objectionable  in  water  for  irrigation 
purposes,  causing  the  accumulation  of  alkali  in  the  soil. 
Permanently  hard  water  affects  the  paper  maker,  the 
tanner,  the  bleacher,  and  the  dyer. 

45.  Filtered   Water.     Thorough   filtering   makes   water 


Fig.  17. — An  effective  sand  filter.     (Drawing  by  Mr.  T.  C.  Hough.) 

more  attractive  for  household  use,  as  color,  odor,  turbidity, 
sediment,  and  to  some  extent,  hardness  may  be  removed 
and  an  infected  water  may  be  made  safer  for  drinking 
purposes.  City  water-supplies  are  often  treated  in  this 
way  and  improved.  Fig.  17  shows  an  effective  sand  filter. 
The  bottom  of  the  filter.  A,  consists  of  puddled  clay  2  feet 
in  thickness,  built  in  with  stones  8  inches  in  thickness; 
layer  B  consists  of  coarse,  angular  stones  and  is  about  30 
inches  in  thickness.  The  next  layer,  C,  consists  of  6  inches 
of  smaller  stones  and  over  this  is  placed  D,  composed  of 


56 


CHEMISTRY  OF  FARM  PRACTICE 


6  inches  of  coarse  gravel,  followed  by  E,  6  inches  of  fine 
gravel.  The  top  layer  consists  of  30  inches  of  sand.  Chan- 
nels (shown  at  X)  are  used  to  collect  the  water;  they  are 
situated  half  in  the  bed  of  clay  and  half  in  the  large  rocks. 
The  best  size  of  sand  to  use  is  0.5-1.0  millimeter  in  diam- 
eter, and  the  greater  the  uniformity  obtained  in  the  size 
of  the  sand  the  better  the  filtration  obtained. 

46.  Boiled  Water.  Water  is  purified  for  drinking  pur- 
poses by  boiling.  This  method  can  easily  be  used  and  is 
quite  inexpensive  and  effective. 


Fig.  18. — A  simple  apparatus  for  distilling  water. 


47.  Distilled  Water.  Distilled  water  is  pure,  but  it 
needs  aeration  to  become  palatable,  as  it  has  a  flat  taste. 
In  Fig.  18  is  shown  an  apparatus  for  distilling  water. 

48.  Boiler  Water.  In  hmestone  regions,  we  find  hard 
water;  in  soils  derived  from  sandstone  and  granite,  soft 
water  occurs.  Water,  however,  does  not  always  partake 
of  the  nature  of  the  topsoil.  Especially  is  this  true  when 
the  sources  of  supply  are  wells,  because  the  water  may  have 
come  in  contact  with  different  strata  below  the  surface. 
If  possible,  water  to  be  used  in  boilers  should  be  analyzed, 
and  a  suitable  supply  selected  before  installing  the  power 
plant;   otherwise  a  hard  crust  or  scale  will  deposit  over  the 


WATER— SOLVENT  ACTION  OF  WATER,  ETC. 


57 


boiler  tubes.  Bicarbonates  and  sulphates  of  calcium  and 
of  magnesium  dissolved  in  water  make  up,  generally,  at 
least  90  per  cent  of  its  hardness.  The  presence  of  the 
two  bicarbonates  constitutes  what  is  known  as  temporary- 
hardness,  which  is  more  easily  handled  than  permanent 
hardness;  the  presence  of  calcium  sulphate  and  of  mag- 
nesium sulphate  constitutes  permanent  hardness. 


Fig.  19. — Scale  removed  from  a  boiler.     (From  lower,  Dec.  22,  1914.) 

The  purification  of  boiler  water  may  be  accomplished 
by  the  methods  given  for  household  water,  page  54. 
Temporary  hardness  may  be  removed  by  heating  the 
supply  in  a  tank  before  it  enters  the  boiler,  by  means  of 
waste  steam  or  by  any  desirable  method.  This  heating 
converts  the  rather  soluble  bicarbonate  of  calcium  or  of 
magnesium  into  the  much  less  soluble  normal  carbonate, 
by  expelling  carbon  dioxide,  according  to  the  following 
formula : 

Ca2H2(C03)3+heat-2CaC03+H20+C02. 


58  CHEMISTRY  OF  FARM  PRACTICE 

The  normal  calcium  carbonate  (CaCOs)  is  soluble  only 
to  the  extent  of  2^  grains  per  gallon.  Magnesium  bicar- 
bonate, when  heated,  decomposes  in  the  same  way  as  cal- 
cium bicarbonate,  although  the  normal  magnesium  car- 
bonate is  soluble  to  the  extent  of  14  grains  per  gallon. 

As  a  second  method,  temporarily  hard  water  may  be 
softened  by  chemical  means  as  already  shown.  Four 
pounds  of  quicklime  will  soften  as  much  water  as  80 
pounds  of  soap,  hence  the  use  of  the  lime  will  be  far  more 
economical.  Needless  to  say,  this  treatment  must  take 
place  in  a  different  receptacle  from  the  boiler.  The  reac- 
tion is  the  same  as  that  previously  given  for  milk  of  lime. 

Pure  calcium  carbonate  does  not  produce  a  very  hard 
scale  at  first,  but  it  hardens  with  heating  and  drying. 
When  it  is  heated  rapidly,  it  deposits  as  mud;  but  when 
heated  slowly  it  forms  calcite,  which  will  become  a  hard 
scale  when  baked.  Magnesiimi  carbonate  behaves  simi- 
larly to  calcium  carbonate. 

Permanently  hard  water  is  less  desirable  as  a  boiler 
supply.  Calcium  sulphate  is  more  troublesome  than  cal- 
cium carbonate,  because  it  forms  a  hard  and  adhesive 
boiler  incrustant,  beneath  which  the  iron  is  often  corroded 
and  overheated. 

Boiler  water  may,  also,  be  helped  by  filtration,  al- 
though the  suspended  matter  strained  out  by  the  filter 
as  a  rule  does  not  cause  a  deposit  of  scale.  One  very 
simple  precaution  may  save  much  trouble,  never  empty  a 
boiler  while  it  is  hot,  because  the  incrustation  in  that  case 
will  be  baked  on.  Never  blow  out  the  boiler  under  steam 
pressure,  because  the  incrustation,  becoming  dry,  absorbs 
carbon  dioxide  from  the  air,  which  helps  to  fix  the  deposit 
more  firmly. 


CHAPTER  VI 


SOIL  WATER 


49.  Water  Requirements  of  Plants.  No  one  factor  has 
a  more  important  bearing  on  crop  production  than  the 
proper  amount  of  the  right  kind  of  soil  moisture.  Table 
IV  has  been  compiled  by  Warrington  from  data  obtained 
by  the  investigators  named  to  show  the  number  of  pounds 
of  water  transpired  by  growing  plants  for  each  pound  of 
dry  matter  produced : 


TABLE  IV. 


-NUMBER  OF  POUNDS  OF  WATER  EVAPORATED 
TO   GROW  CROPS  ENUMERATED 


Lawes  and  Gilbert, 
England. 

Hellriegel, 
Germany. 

Wollny 
Germany. 

King, 
Wisconsin. 

Beans 214 

Beans 262 

Maize 233 

Maize 272 

Wheat....  225 

Wheat....  359 

Millet....  416 

Potatoes.  .  423 

Peas 235 

Peas 292 

Peas 479 

Peas 447 

Red  clover.  249 

Red  clover  330 

Rape 912 

Red  clover  453 

Barley 262 

Barley. ...   310 

Barley 774 

Barley. ...   393 

Oats 402 

Oats 665 

Oats 557 

Buckwheat  371 

Buckwheat  664 

Lupine .  .  .  373 

Mustard..    843 

' 

Rye 377 

Sunflower.  490 

In  general,  it  may  be  stated  that  from  200  to  500  pounds 
of  water  are  required  to  produce  1  pound  of  dry  matter 
of  the  ordinary  field  crops.  The  amount  required  is  in- 
fluenced by  the  climate,  the  soil  type,  and  the  preparation 
and  cultural  methods  employed. 

50.  Soil  Components.  The  soil  is  made  up  of  three 
components,   solid,   liquid,   and   gaseous.    The  solid   part 

69 


60  CHEMISTRY  OF  FARM  PRACTICE 

consists  of  the  inorganic  and  organic  materials;  the  liquid 
part  consists  of  water  carrying  more  or  less  of  mineral  or 
of  organic  materials  in  solution;  the  gaseous  part  consists 
of  air,  mixed  with  carbon  dioxide  produced  by  the  decom- 
position of  organic  matter,  water  vapor  and  other  gases. 
The  whole  may  be  likened  to  an  animal,  the  solid  part 
forming  the  body,  the  skeleton  of  which  represents  the 
inorganic  solids,  while  the  flesh  and  muscles  represent 
the  organic  solids;  the  soil  water  and  its  contents  con- 
stituting the  circulatory  system  of  the  animal,  and  the 
air  and  other  gases  the  respiratory  system. 

51.  Soil  Water.  All  plant  food  that  enters  the  plant 
from  the  soil  is  transferred  to  the  plant  in  solution ;  there- 
fore, we  see  that  the  plant  food  in  the  soil  must  become 
soluble  in  the  soil  water  before  the  plant  can  use  it  for  the 
building  of  its  tissues.  It  is  a  wise  provision  of  nature 
that  the  better  treatment  of  the  land  accentuates  the 
factors  that  promote  solution,  while  poor  methods  of  soil 
treatment  make  the  plant  food  elements  less  soluble. 

The  rainfall  of  the  different  sections  of  the  United 
States  is  variable,  ranging  from  about  100  inches  in  the 
nlost  humid  areas  to  as  low  as  from  2  to  5  inches  in  the 
most  arid  regions.  The  rainfall  most  desirable  for  maxi- 
mum production  is  about  50  inches.  When  rainfall  is 
less,  there  is  more  reason  for  greater  efforts  toward  con- 
servation of  moisture. 

There  are  three  forms  of  water  in  the  soil:  Gravitational, 
capillary,  and  hygroscopic.  The  gravitational  or  free  water 
moves  under  the  force  of  gravity.  Generally  it  is  more 
harmful  than  helpful,  because  it  leaches  soluble  plant  food, 
excludes  the  air,  hinders  bacterial  action,  reduces  surface 
tension,  and  dissolves  cementing  materials.  It  is  helpful 
to  the  extent  that  it  is  converted  into  the  capillary  form. 
Also  it  may  serve  to  wash  some  harmful  bodies  out  of 
the  soil. 

The  capillary  moisture  is  the  hquid  film  which  surrounds 


SOIL  WATER 


61 


soil  particles.     This  form  of  moisture  furnishes  the  plant 
with  almost  its  entire  supply  of  Uquid  food.     When  capillary 


w 
n 


a. 


o 


a 
^ 


o 


action  is  promoted  by  favorable  conditions  of  the  soil, 
moisture  may  be  drawn  up  from  the  water  table  some 
distance  below,  the  amount  of  rise  being  determined  by 


62  CHEMISTRY  OF  FARM  PRACTICE 

the  cross-section  area  of  the  capillary  spaces  and  by  the 
strength  of  the  liquid  film  at  the  upper  surface  of  these 
spaces.  The  smaller  the  area  of  the  capillaries  the  greater 
will  be  the  distance  through  which  the  water  will  rise. 

Every  care  should  be  exercised  to  increase  the  supply 
of  moisture  by  the  prevention  of  evaporation  and  per- 
colation. The  available  moisture  is  increased  and  the 
surface  washing  is  decreased  by  deeper  preparation  of 
the  soil,  which  offers  a  larger  reservoir  for  the  retention  of 
water.  Then,  too,  surface  washing  can  be  greatly  lessened 
by  the  practice  of  terracing,  which  is  quite  extensively 
used  in  the  Southern  States,  and  also  by  the  use  of  rotations 
that  do  not  have  many  clean-cultured  crops  in  them.  The 
evaporation  can  be  greatly  lessened  by  shallow  cultivation, 
during  the  growing  season,  which  serves  to  form  a  soil 
mulch,  destroys  the  surface  capillarity,  and  retains  moisture 
very  effectively.  The  retention  of  the  largest  possible 
amount  of  the  moisture  serves  a  two-fold  purpose:  It  adds 
to  the  available  moisture,  which  is  often  the  limiting  factor 
of  production,  and  it  lessens  the  surface  washing.  In  no 
way  are  our  clean-cultured,  rolling  lands  depleted  more 
than  by  surface  washing,  and  its  prevention  is  worthy  of 
the  close  consideration  of  those  who  own  or  cultivate  such 
lands. 

For  best  soil  conditions,  the  gravitational  water  should 
sink  deep  into  the  soil  as  rapidly  as  possible,  in  order  that 
the  capillary  action  may  be  at  its  best.  Where  the  drain- 
age is  good,  the  gravitational  water  is  no  trouble.  Deep 
fall  plowing,  the  incorporation  of  organic  matter,  and  com- 
paratively shallow  cultivation  after  each  rain,  in  order  to 
form  a  soil  mulch,  are  the  secrets  of  the  conservation  of 
moisture. 


CHAPTER   VII 

AIR  IN  SOILS 

52.  Composition  of  the  Atmosphere.  The  atmosphere 
consists  mainly  of  a  mixture  of  the  two  gases,  nitrogen 
and  oxygen,  and  contains  in  addition  argon,  variable  quan- 
tities of  aqueous  vapor,  and  very  small  amounts  of  carbon 
dioxide,  ammonia,  hydrogen,  and  ozone.  Under  certain 
conditions  other  gases,  certain  salts,  finely  divided  soil 
particles,  and  sm±all  particles  of  animal  and  vegetable  matter 
may  occur  as  incidental  ingredients.  Dry  air  contains  about 
75^  per  cent  by  weight  of  nitrogen,  and  about  23  per  cent 
by  weight  of  oxygen,  the  other  elements  and  compounds 
mentioned  being  present  in  very  small  quantities  in  mois- 
ture-free air.  Carbon  dioxide  is  present  on  an  average 
in  the  proportions  of  4  parts  of  carbon  dioxide  to  10,000 
parts  of  air.  This  seems  insignificant,  but  the  tremendous 
weight  of  the  atmosphere  can  be  realized  when  we  con- 
sider that  this  minute  proportion  is  equivalent  to  28  tons 
of  carbon  dioxide  in  the  atmosphere  over  one  acre  of  land. 
The  atmosphere  is  continuously  moving,  so  that  the  air 
over  an  acre  of  land  is  renewed  many  times  during  the 
course  of  a  day,  thus  tending  to  keep  the  air,  although  a 
mixture,  approximately  of  definite  composition.  Growing 
crops  rapidly  use  up  carbon  dioxide  in  the  process  of  build- 
ing up  the  plant  structures,  all  of  which  are  largely  car- 
bonaceous. The  ratio  between  oxygen  and  carbon  dioxide 
is  kept  constant,  the  amount  of  oxygen  used  up  by  com- 
bustion and  life  processes  being  restored  by  the  decomposi- 
tion of  carbon  dioxide  by  the  chlorophyl  of  the  growing 
plant  and  the  discharge  into  the  air  of  the  oxygen  thus 
produced. 

63 


64 


CHEMISTRY  OF  FARM  PRACTICE 


The  free  nitrogen  present  in  the  air  is  inert  and  can- 
not be  made  use  of  by  the  plant  directly  for  plant  food. 
Certain  parasitic  micro-organisms  living  on  the  roots  of 
plants  have  the  power  of  converting  the  nitrogen  of  the 
air  into  a  form  which  becomes  available  as  plant  food,  as 
stated  on  page  38.  There  is  another  class  of  bacteria 
that  live  on  decaying  organic  matter,  which  has  the  power 


Fig.  21. — Texture  of  a  typical  bright  tobacco   land  of  Virginia  and 
North  Carohna.     (U.  S.  Dept.  Agr.) 


of  "  fixing  "  atmospheric  nitrogen 
come  available  for  plant  growth, 
on  decaying  organic  matter  are  said 
53.  Soil  Air.     The  composition 
upon  the  amount  of  organic  matter 
with   which  it  is  decaying.     The 
differs  considerably  from   that    of 


in  a  form  that  may  be- 
The  bacteria  that  live 

to  be  saprophytic. 

of  the  soil  air  depends 

present  and  the  rapidity 

composition   of  soil   air 
the    atmosphere.     The 


AIR  IN  SOILS  65 

volume  of  air  contained  in  different  soils  is  quite  variable, 
and  is  affected  by  the  soil  structure,  texture,  organic  matter 
and  moisture  content. 

The  greatest  changes  in  the  composition  of  soil  air 
are  found  in  the  air  of  clayey  soils  when  the  particles  are 
extremely  small.  Clay  particles  may  be  flocculated  into 
masses,  or  flocculated  clay  may  be  granulated,  thus  con- 
siderably changing  the  pore  space  in  the  soil  and  the  volume 
of  air  that  it  will  contain. 

The  size  of  the  soil  particles,  which  determines  texture, 
also  affects  the  pore  space  and,  consequently,  the  air  con- 
tent of  the  soil.  Soil  particles  are  of  varying  sizes,  and 
under  field  conditions,  the  soils  of  fine  texture  generally 
possess  large  air  space. 

Organic  matter  is  quite  porous,  and  its  effect  in  the 
soil  is  always  to  increase  the  volume  of  air.  It  is  necessary 
to  have  a  sufficient  supply  of  air  to  promote  the  decay 
of  organic  matter.  The  main  benefits  of  organic  matter 
are  gained  through  its  decay. 

The  more  completely  the  pore  spaces  in  soils  are  filled 
with  water,  the  smaller  the  amount  of  air  that  will  be  pres- 
ent. Water  is  held  by  capillary  attraction  more  securely 
when  the  particles  are  small  than  when  large,  the  capillarity 
being  greater  in  a  soil  of  comparatively  fine  texture.  The 
volume  of  air  increases  and  the  capillary  water  diminishes 
when  larger  particles  or  granules  are  present.  Because 
of  this  the  flocculation  of  the  clay  soils  of  bottom  lands 
by  the  use  of  lime  permits  of  better  drainage  and  more 
complete  aeration,  thus  greatly  improving  this  type  of 
soil. 

54.  Effect  of  Carbon  Dioxide  on  Decay.  The  very  rapid 
decay  of  organic  matter  and  the  liberation  of  carbon  dioxide 
in  large  volume  might  serve  to  decrease  the  rapidity  of 
decay  on  account  of  the  harmful  effect  of  large  percentages 
of  carbon  dioxide  to  certain  of  the  organisms  producing 
decay.     The    percentage    of    carbon    dioxide   liberated    in 


66  CHEMISTRY  OF  FARM  PRACTICE 

the  soil  is  proportional  to  the  rapidity  with  which  the 
organic  matter  decomposes;  for  carbon  dioxide  is  one  of 
the  main  products  of  the  decay  of  organic  matter.  Decay 
goes  on  most  rapidly  during  the  warm  months  of  the  year, 
when  the  crop  is  being  produced.  At  the  time  that  soil 
moisture  will  be  most  highly  charged  with  carbon  dioxide 
and  its  solvent  powers  most  increased,  plant  food  is  most 
needed.  It  has  been  proved  that  the  plant  rcDts  absorb 
oxygen  and  give  off  carbon  dioxide,  which  action  has  a 
tendency  to  increase  the  solvent  power  of  the  soil  moisture 
in  the  immediate  vicinity  of  the  roots. 

The  formation  of  carbonates  by  the  reaction  between 
soil  bases  and  carbonic  acid  may  be  beneficial  to  the  soil, 
as  in  the  case  of  carbonate  of  lime,  and,  in  moderate  quan- 
tities, carbonate  of  magnesium.  On  the  other  hand,  large 
quantities  of  the  carbonates  of  sodium  and  of  potassium 
are  deleterious,  as  is  seen  in  the  alkali  lands  of  the  West. 
There  is  a  tendency  for  carbonates  of  sodium  and  of  potas- 
sium to  deflocculate  the  clay  and,  consequently,  harm- 
fullj'  affect  the  tilth  of  the  soil. 

55.  Oxygen  Must  be  Present.  The  oxygen  of  the  air 
is  very  important  in  its  effects;  the  process  of  decay  is  in 
reality  oxidation.  Some  mineral  compounds  are  oxidized, 
and  their  solubilities  changed.  Most  vegetable  materials 
ai*e  oxidized  during  the  process  of  decay,  the  ash  elements 
contained  being  brought  into  solution  so  that  they  may 
be  made  use  of  by  growing  plants,  and  carbon  dioxide  is 
hberated,  which,  in  turn,  promotes  the  availability  of 
insoluble  plant  food  from  the  mineral  materials.  Oxygen 
is  necessary  for  the  germination  of  seeds,  the  growth  of 
plant  roots,  and  in  combination  with  carbon  as  CO2  for 
the  formation  of  the  carbohydrates  stored  up  in  plant 
structures. 

56.  Factors  Affecting  Soil  Air.  The  air  content  of  the 
soil  is  affected  by  several  factors.  In  the  first  place,  there 
is  an  exchange  of  air  between  the  air  above  the  soil  and 


AIR  IN  SOILS 


67 


the  air  within  the  soil.  They  come  together  at  the  sur- 
face of  the  ground,  and  this  exchange  is  brought  about  by 
diffusion,  which  is  dependent  upon  the  pore  space  within 
the  soil. 

Diffusion  is  the  mingling  of  gases  into  each  other.  It 
may  be  measured  by  the  passage  of  a  gas  through  a  porous 
partition.     It   has   been    demonstrated   that   the   rate   of 


Porous  Cup 


-Hydrogea 


Fio.  22. — Diffusion  of  hydrogen  through  a  porous  cup. 


diffusion  of  a  gas  is  inversely  proportional  to  the  square 
root  of  the  density  of  a  gas.  The  rapidity  of  diffusion 
may  be  shown  by  the  apparatus  in  Fig.  22.  Hydrogen 
surrounding  the  unglazed  porcelain  cup  and  air  within 
it  each  diffuse  through  the  pores  of  the  cup,  but  the  air, 
being  nearly  sixteen  times  as  dense  as  hydrogen,  will  dif- 
fuse one-fourth  as  rapidly.  The  hydrogen  will  penetrate 
to  the  interior  of  the  cup  more  rapidly  than  the  air  can 
diffuse  outward,  consequently  there  will  be  increased  pres- 


68  CHEMISTRY  OF  FARM  PRACTICE 

sure  within  the  cup,  which  will  exert  pressure  upon  the 
water  in  the  connecting  bottle,  forcing  it  in  a  spray  from 
the  tube.  Should  the  bell  jar  with  its  hydrogen  atmosphere 
now  be  removed,  the  hydrogen  which  now  is  within  the 
cup  will  diffuse  rapidly  into  the  outside  air  and  the  de- 
creased pressure  within  the  cup  will  be  indicated  by  bubbles 
of  air  rising  from  the  tube  through  the  water  in  the  bottle. 

Thorough  tillage  enlarges  the  pore  space  and  aids  dif- 
fusion; packing  a  soil  decreases  the  pore  space  and  the 
diffusion.  When  rain  falls,  the  water  fills  much  of  the 
pore  space,  excluding  a  certain  volume  of  air;  but,  as  the 
water  sinks  into  the  soil,  the  air  is  forced  after  it,  because 
of  the  pressure  of  the  atmosphere  above,  filling  the  space 
made  vacant  by  the  sinking  of  the  water.  The  volume 
of  a  gas  is  directly  proportional  to  the  temperature  and  in- 
versely proportional  to  the  pressure.  The  warmer  the  tem- 
perature, the  greater  the  volume  of  any  gas,  and  the  greater 
the  pressure,  the  smaller  will  be  the  volume  occupied  by 
a  given  gas.  Under  climatic  conditions,  there  are  con- 
stant changes  of  both  temperature  and  pressure,  which 
bring  about  movement  of  the  soil  atmosphere. 

57.  Means  of  Producing  a  Change  of  Soil  Air.  The 
means  at  our  disposal  to  produce  change  of  soil  air  are 
tillage,  underdrainage,  rotation,  manures,  and  lime. 

Thorough  tillage  induces  more  exchange  of  air  between 
the  atmosphere  above  the  surface  and  the  air  beneath  the 
surface.  Underdrainage  removes  superfluous  water  and  in- 
creases the  pore  space  that  is  filled  by  air,  thus  allowing 
a  freer  circulation  within  the  soil.  Irrigation  induces  change 
in  soil  air  in  the  same  manner  that  rain  induces  change. 
The  influx  of  water  to  a  large  extent  excludes  the  air  from 
the  soil,  and,  as  the  water  sinks  into  the  soil,  the  pore 
space  is  refilled  with  air.  Rotation  of  crops  aids  in  the 
proper  aeration  of  a  soil,  because  the  root  systems  of  the 
different  crops  grown  in  the  rotation  are  confined  to  dif- 
ferent soil  strata,   and,   as  old  roots   decay  through  the 


AIR  IN  SOILS  69 

process  already  mentioned,  air  passages  are  formed  in 
the  soil.  Animal  manures  exert  an  influence  on  the  texture 
of  the  soil,  which  enlarges  the  pore  space.  Applications  of 
lime  affect  the  structures  of  certain  soils  very  materially, 
causing  a  rearrangement  of  the  soil  particles  in  such  a 
way  as  to  open  the  soil  to  an  appreciable  extent. 


CHAPTER  VIII 
THE  ASSIMILATION  OF  PLANT  FOOD 

58.  Source  of  Plant  Food.  The  plant  derives  its  food 
from  two  sources — the  atmosphere  and  the  soil.  By  far 
the  greater  portion  is  obtained  from  the  atmosphere.  Of 
the  ten  elements  necessary  for  plant  growth — carbon,  hy- 
drogen, oxygen,  nitrogen,  phosphorus,  potassium,  sulphur, 
iron,  calcium,  and  magnesium — carbon,  hydrogen,  and 
oxygen  compose  about  95  per  cent  of  all  agricultural  crops. 
These  three  elements  are  supplied  from  the  atmosphere. 
Some  of  the  nitrogen  used  by  plants  is  also  derived  indi- 
rectly from  the  atmosphere,  from  which  it  is  "  fixed  "  by 
means  of  bacteria  (see  page  38).  The  soil  elements  nec- 
essary for  plant  growth  are  taken  up  by  the  plants  from 
water  solution.  The  root  system  of  the  plant  constitutes 
the  channels  for  taking  up  the  solutions. 

According  to  their  root  systems,  plants  may  be  divided 
into  two  main  classes,  those  that  have  tap  roots  and  those 
that  have  a  mass  of  lateral,  fbrous  roots.  The  tap-rooted 
plants  usually  penetrate  deeper  into  the  soil.  The  main 
roots  of  the  former  class  have  smaller  branches,  and  these, 
in  turn,  are  covered  with  root  hairs  (Fig.  24)  which  are  cells 
that  act  like  syphons.  They  consist  of  cells  which  contain 
granular  protoplasm  and  sap.  These  root  hairs  jare  widely 
distributed  throughout  the  soil,  and  come  in  intimate  con- 
tact with  the  soil  particles.  The  soil  particles  are  covered 
with  capillary  moisture  containing  certain  amounts  of 
plant  food  which  has  been  dissolved  from  the  particles. 
This  moisture  with  its  dissolved  material  is  taken  up  by 
the  root  hairs  and  conveyed  by  osmotic  pressure  into  the 

70 


THE  ASSIMILATION  OF  PLANT  FOOD 


71 


plant.  The  portion  of  the  plant  root  that  is  covered  with 
root  hairs  does  not  elongate.  The  root  elongates  from 
the  growing  tip. 


Fig.  23. — The  root  system  of  a  corn  plant  to  a  depth  of  three  feet. 
(From  McCall's  "  Studie.s  of  Soils.") 

59.  Osmosis.  AVhen  two  solutions  are  separated  by  a 
membrane,  the  weaker  solution  will  flow  towards  the  stronger 
solution,  because  water  readily  passes  through  the  membrane, 


72 


CHEMISTRY  OF  FARM  PRACTICE 


while  the  solution  containing  the  greater  amount  of  material 
will  flow  more  slowly,  being  obstructed  by  the  membrane. 
The  inflow  of  water  into  the  plant  is  thought  to  be  in  re- 
sponse to  the  pressure  thus  generated,  the  cell  waJl  of  the 
root  hair  being  the  membrane  and  the  sap  within  the  cell 


is 


Fig.  24.— (a)  Root  hairs,  (6) 
close  contact  of  root  hairs 
with  soil  particles. 


Fig.  25. — Osmosis  shown  with 
a  bladder  membrane. 


being  more  concentrated  than  the  soil  solution.  The  dif- 
fusion of  the  plant  food  from  cell  to  cell  throughout  the 
plant  is  considered  to  be  due  to  the  same  cause. 

Every  element  or  compound  in  the  soil  solution  has 
its  specific  relationship  to  osmosis  and,  in  this  way,  the 
amount    of    ea«h    material    imbibed    is    governed.     Some 


THE  ASSIMILATION  OF  PLANT  FOOD  73 

excretions  due  to  the  slow  passage  of  the  denser  Hquid 
from  the  plant  take  place  through  the  root  hairs,  but  this 
is  very  small  considering  the  amount  taken  in,  the  greater 
quantity  going  to  the  side  of  the  stronger  solution,  i.e., 
into  the  plant.  The  solution  containing  the  plant  food 
finds  its  way  through  the  stems  of  the  plant  to  the  leaves; 
there  it  comes  into  the  "  laboratory  "  of  the  plant,  and 
in  contact  with  the  elements  derived  from  the  atmosphere. 

60.  Function  of  the  Leaves  of  Plants.  The  water 
which  serves  as  the  carrier  of  plant  food  from  the  soil 
originally  comes  from  the  atmosphere  in  the  form  of  rain 
water.  Carbon  diox'.de  comes  from  the  atmosphere,  and 
is  taken  into  the  plant  through  small  openings  in  the  leaf, 
known  as  the  stomata.  The  stomata  form  the  breathing 
pores  of  the  plants.  Through  them  carbon  dioxide  is  taken 
into  the  plant  and  oxygen  is  given  off.  In  the  leaves  of 
the  plant,  all  of  the  various  elements  of  plant  food  are 
brought  together  and  are  built  up  into  the  proximate  con- 
stituents of  the  plant.  This  process  is  termed  'photosyn- 
thesis. Photosynthesis  takes  place  only  in  plants  which 
contain  green  coloring  matter.  The  material  that  produces 
the  green  coloring  of  plants  is  known  as  chlorophyl. 

The  simplest  photosynthesis  is  that  in  which  formalde- 
hyde is  produced.  This  is  made  into  carbohydrates.  The 
process  is  accomplished  in  the  leaves  of  the  plants  under 
the  influence  of  chlorophyl,  sunlight,  and  aqueous  carbon 
dioxide.     It  may  be  expressed  in  chemical  equation : 

C02+H20-CH20-f-02, 
6CH20  =  C6Hi206. 

Carbon  dioxide  and  water  yield  formic  aldehyde  (CH2O) 
and  oxygen.  The  oxygen  given  off  serves  to  replenish 
the  atmosphere  and  aids  in  maintaining  the  balance  be- 
tween plant  and  animal  life.  Six  molecules  of  formic 
aldehyde,  by  condensation,  form  sugar  (C6H12O6).  The 
sugars  are  soluble,  and  it  is  in  this  form  that  the  carbo- 


74 


CHEMISTRY  OF  FARM  PRACTICE 


hydrates  are  transported  to  different  parts  of  the  plant, 
where  they  lose  water,  according  to  the  reaction 

C6H12O6  =  C6H10O5+H2O. 

The  material  is  then  stored  in  the  form  of  insoluble  starch 
(CeHioOs). 

The  formation  of  the  proteid  compounds  (nitrogenous) 
is  more  complex,  but  it,  too,  is  carried  on  in  the  laboratory 
of  the  plant,  the  leaves.  The  rapidity  of  growth  is  dependent 
upon  leaf  area.  This  fact  should  be  carefully  considered, 
and  too  close  clipping  of  grass  in  pastures  should  be  avoided, 
because  such  cropping  lessens  the  size  of  the  factory  that 
is  building  more  grass. 

61.  Leaching.  It  has  been  shown  that  some  of  the 
plant  food  may  be  leached  out  of  the  plant  into  the  soil 
by  rains,  and  may  possibly  again  be  made  use  of  by  the 
same  plant  for  the  development  of  other  parts  of  the  plant. 
Hopkins  gives  the  following  tabular  extracts  from  Le 
Clerc's  lectures  on  this  subject: 


TABLE  v.— PLANT  FOOD  REMOVED  FROM  PLANTS  BY 
LEACHING  WITH  WATER  ON  BASIS  OF  PER  CENT  OF 
TOTAL  CONTENT 


Plants  Leached. 


Wheat,  in  early  bloom 

Wheat,  fairly  ripe 

Wheat,  dead  ripe 

Oats,  from  8  ins.  in  height  to  ripe- 
ness; total  removed  by  repeated 
leaching 

Potato  vines 


1 

7 
25 


0 
33 
21 


33 
50 


4 
54 
65 


36 
30 


10 
46 

58 


45 
12 


0 
34 
55 


40 
9 


12 
41 
56 


23 
30 


60 
90 


40 
50 


THE  ASSIMILATION  OF  PLANT  FOOD  75 

Similar  experiments  have  been  conducted  by  German 
investigators.  These  investigations  show  that  little  plant 
food  is  leached  during  the  early  stages  of  growth, 
but  that  there  is  considerable  leaching  as  the  ripening 
proceeds. 


CHAPTER   IX 

THE   FORMATION,   COMPOSITION,   AND   FERTILITY   OF 

SOILS 

62.  Formation  of  Soil.  At  one  period  in  the  liistory  of 
the  earth,  its  entire  crust  was  igneous  rock.  Many  agencies 
have  been  working  through  untold  ages  to  develop  the 
soil  into  its  present  condition.  The  weathering  of  rock 
has  proceeded  at  different  rates,  being  governed  by  the 
,  activities  of  the  agencies  involved.  Weathering  is  brought 
about  by  chemical,  physical,  and  biological  means.  The 
•^agencies  of  weathering  are  the  atmosphere,  water,  heat, 
cold,  gravitation,  electrical  discharges,  and  organisms. 

The  chief  action  of  the  atmosphere  is  chemical,  brought 
about  mainly  through  oxidation  and  the  solvent  effects 
of  carbon  dioxide  in  solution.  The  atmosphere  also  exerts 
physical  influences  that  hasten  rock  decay.  Winds  blow 
particles  against  other  particles,  producing  abrasion,  and 
by  blowing  against  trees  and  plants,  cause  them  to  act 
as  levers,  which  press  the  soil  particles  against  each  other, 
thus  causing  them  to  grind  and  wear  one  another  away. 

Water,  in  addition  to  its  solvent  action,  has  a  physical 
influence  on  the  soil,  in  that  rainfall  causes  the  rubbing 
together  of  soil  particles,  thus  producing  some  erosive  effect. 
Surface  water  causes  the  wearing  of  soil  particles  against 
each  other  and  thus  increases  their  fineness.  The  erosion 
of  the  land  tends  to  reduce  the  soil  nearer  to  a  base  level. 

Heat  and  cold  have  the  same  physical  effects  on  rocks 
that  they  have  on  other  substances,  rocks  expanding  when 
heated  and  contracting  on  cooling.  The  units  which  go 
to  make  up  rocks  are  minerals.  Different  minerals  have 
different  rates  of  expansion  and  contraction,  consequently, 

76 


f^OIL  FORMATION,  COMPOSITION,  ETC. 


»f»'-'"'»^--i>: 


78  CHEMISTRY  OF  FARM  PRACTICE 

when  sudden  changes  of  temperature  occur,  there  is  a 
tendency  to  break  up  the  rock.  The  surface  of  the  rock 
is  subjected  to  more  rapid  changes,  due  to  outside  influence 
of  heat  and  cold,  and  this  influence  tends  to  form  flakes, 
cracks,  and  crevices,  even  on  the  outer  surface  of  the  same 
mineral.  Water  is  retained  in  the  cracks  and  crevices,  and 
exerts  its  solvent  influences.  Then  also,  when  water  cools, 
it  first  contracts,  becoming  densest  at  4°  Centigrade,  then 
expands  till  the  temperature  falls  to  zero.  These  changes 
of  volume  tend  to  break  up  rocks.  When  the  water  freezes, 
there  is  a  sudden  expansion  by  which  such  enormous  pres- 
sure may  be  exerted  as  to  shatter  the  strongest  rocks. 

After  soib  is  formed  in  the  crevices  of  rocks,  plants 
grow,  and  the  roots  of  these  plants  have  a  solvent  effect 
on  the  rock,  due  to  the  excretion  of  sap.  Later,  when 
more  soil  has  formed,  trees  may  grow  between  the  rock 
masses,  exerting  a  powerful  force  tending  to  separate  the 
masses.  In  addition  to  this  action  of  plants  and  trees 
in  separating  masses  of  rock,  minute  plant  organisms,  such 
as  Uchens  and  mosses,  grow  on  rock  surfaces  and  form  soil 
which  is  either  washed  off  or  deepens  until  it  furnishes  a 
home  for  higher  orders  of  plants,  which  in  turn  are  followed 
by  trees.  These  growing  trees  and  plants  get  their  plant 
food  from  deep  down  in  the  soil,  and  drop  their  leaves  on 
the  surface  of  the  ground.  The  decay  of  these  leaves 
impregnates  the  soil  moisture  with  carbon  dioxide,  in 
which  condition  it  has  a  much  greater  solvent  effect  on 
the  mineral  portion  of  the  soil  underneath.  The  soil  layer 
is  thus  continuously  deepened  through  additional  deposits 
above  and  the  continued  solution  of  the  rock  beneath. 

Glaciers  have  exerted  in  past  ages  a  powerful  influence 
on  soil  formation.  These  vast  ice  fields  crept  slowly  south- 
ward, grinding  the  rocks  beneath  them  to  a  condition  of 
great  fineness.  Some  of  the  richest  soils  of  the  world  are 
of  glacial  origin. 

Rivers  emptying  into  the   ocean,   on   account  of  the 


SOIL  FORMATION,  COMPOSITION,  ETC. 


79 


checking  of  the  current  and  the  action  of  the  salts  in  the 
sea  water,  deposit  the  materials  carried  in  suspension.  1  hese 
materials  gradually  accumulate  on  shallow  bottoms  until 
marsh  lands  are  formed,  and  the  building  is  continued 
through  the  action  of  winds,  waves,  tides,  and  plants  until 
soil  is  gradually  formed.  There  are  many  organisms  in 
the  ocean,  such  as  coral  polyps  and  shell-fish,  that  build 
up  islands.  The  sea  bottom  is  the  seat  of  many  soil- 
forming  activities,  and  vast  areas  of  sea  bottom  have  been 


Fig. 


27. — Residual    soil,    Piedmont    region.     (By    permission    F. 
Tarbox,  S.  C.  Exp.  Station.) 


G. 


elevated  to  form  some  of  our  most  fertile  soils.  Sandstones, 
shales,  and  marls  are  formed  at  the  bottom  of  the  ocean. 

63.  Composition  of  Soils.  About  ninety-ei^ht  per  cent 
of  the  earth's  solid  crust  consists  of  the  eight  elements: 
oxygen,  silicon,  aluminium,  iron,  calcium,  potassium,  sodium, 
and  magnesium,  here  arranged  in  the  order  of  their  abun- 
dance. These  elements  make  up  the  common  minerals, 
which,  in  turn,  make  up  the  common  rocks. 

The  difference  in  the  chemical  composition  of  different 
soils  is  due  to  the  differing  compositions  of  the  rocks  from 


80 


CHEMISTRY  OF  FARM  PRACTICE 


SOIL  FORMATION,  COMPOSITION,  ETC.  81 

which  the  soils  are  derived,  the  method  of  rock  decay, 
and  the  conditions  under  which  it  has  existed  since  its 
formation.  The  soils  that  have  remained  where  they  were 
originally  formed  are  of  two  kinds,  residual  and  cumulose, 
the  latter  being  the  result  of  the  accumulations  of  plant 
residues.  The  residual  soil  is  the  result  of  rock  decay, 
and  represents  the  portions  of  the  products  that  remain 
on  the  parent  rock.  This  consists,  in  a  large  measure,  of 
the  elements  most  insoluble,  which,  however,  represent  but 
a  small  part  of  the  original  rock.  There  is  very  little  car- 
bonate of  lime  in  residual  soils;  even  those  derived  from 
limestone  rock  are  often  deficient  in  calcium  carbonate, 
the  soil  itself  being  simply  the  remains  of  the  impurities 
in  the  original  limestone  rock.  The  carbonate  of  lime  has 
been  converted  into  soluble  calcium  bicarbonate,  when  it 
has  come  in  contact  with  water  containing  carbon  dioxide, 
and  then  it  is  leached  out  of  the  rock.  Soils  derived  from 
granite  or  gneiss  are  generally  of  a  clayey  nature.  Soils 
from  marine  formations  are  often  sandy.  Both  classes 
grade  into  clay  loam  or  sandy  loam  as  the  case  may  be. 

The  transported  soils  are  formed  from  the  products  of 
rock  decay  mixed  with  a  certain  amount  of  organic  matter. 
These  materials  have  been  transported  from  the  place  where 
they  were  formed  by  such  agencies  as  water,  ice,  wind, 
and  gravity.  Their  composition  will  vary  to  a  consid- 
erable degree. 

"  Soils  that  have  been  transported  by  water  are  classified 
as  marine,  alluvial,  and  lacustrine.  Marine  soil  is  formed 
by  the  deposits  in  the  ocean  beds,  which  are  subsequently 
elevated.  Alluvial  soils  are  formed  by  the  deposition  of 
material  along  the  shores  of  streams,  and  are  very  variable 
in  composition.  Lacustrine  soils  are  formed  in  the  beds 
of  lakes  or  ponds  which  are  subsequently  drained. 

The  wind-borne,  or  aeolian,  soils  are  rather  extensively 
represented  by  the  loess  soils  of  the  central  parts  of  the 
United  States.     This  wind- deposited  soil  covers  to  varying 


82 


CHEMISTRY  OF  FARM  PRACTICE 


depths  parts  of  the  Mississippi  basin.  The  loess  deposits 
extend  from  IlUnois  and  Iowa  as  far  south  as  some  parts 
of  Mississippi. 


Fig.    29. — Saproph5rtic    plants    called    "  frog   stools "    indicate    that 
decaj  has  begun.     (Farmers'  Bulletin  468,  U.  S.  Dept.  Agr.) 

The  gravity-moved  soils  are  termed  colluvial,  and  are 
not  very  extensive. 

64.  Gain  and  Loss  of  Plant  Food.  Two  sets  of  factors 
affect  the  fertility  of  soil,  both  of  which  may  be  modified 


SOIL  FORMATION,  COMPOSITION,  ETC.  83 

by  artificial  means.  One  set  of  factors  tends  to  impoverish 
the  soil;  the  other  set  is  constructive.  It  is  necessary 
to  distinguish  those  factors  which  exhaust  the  soil  from 
those  which  build  it  up,  and  to  know  how  to  minimize  the 
former  and  to  magnify  the  latter.  In  the  natural  state, 
there  usually  is  a  process  of  enrichment  due  to  the  accu- 
mulation of  plant  food  elements  in  the  surface  soil.  These 
elements  are  left  in  the  residues  of  decaying  organic  matter. 
In  the  process  of  decay,  the  organic  matter  furnishes  food 
for  myriads  of  bacteria,  some  of  which  have  the  power  of 
fixing  the  nitrogen  of  the  atmosphere  in  a  form  that  plants 
can  make  use  of  for  their  growth.  These  organisms  must 
not  be  confused  with  the  bacteria  that  exist  in  symbiotic 
union  with  legumes,  and  fix  nitrogen  in  such  a  form  that 
either  the  legume  or  a  companion  crop  may  make  use  of 
it.  The  bacteria  on  legumes  grow  on  living  plants,  and 
may  be  termed  parasitic  in  their  mode  of  life,  while  the 
bacteria  that  live  on  dead  tissues  may  be  termed  saprophytic. 
There  is  a  point  reached  in  the  accumulation  of  plant  food 
in  the  soil  from  the  plant  residues  at  which  the  increase 
and  the  loss  in  plant  food  about  balance,  due  to  loss  through 
leaching. 

65.  Importance  of  the  Rotation  of  Crops.  When  land 
is  planted  to  clean-cultured  crops,  two  sets  of  losses  to  the 
soil  are  operative;  one,  due  to  the  amount  of  plant  food 
removed  in  the  crop,  and  the  other  due  to  the  increased 
rapidity  of  nitrification  brought  about  by  cultivation,  and 
consequently,  increased  losses  through  leaching. 

There  are  advantages  incidental  to  rotation.  It  is  a 
well-established  (act  that  some  plants  take  up  greater 
amounts  of  some  elements  than  do  others;  that  some  plants 
possess  the  power  of  taking  their  food  from  compounds  that 
others  are  powerless  to  use.  Some  plants  have  a  longer 
growing  season  than  others,  and  although  they  may  take 
as  much  food  from  the  soil,  yet  the  drain  is  lighter,  owing 
to  the  longer  growing  season.     The  root  systems  of  plants 


84 


CHEMISTRY  OF  FARM  PRACTICE 


differ  considerably,  and  the  area  occupied  by  the  root 
system  hmits  the  area  from  which  the  plants  feed.  The 
cultivation  of  crops  differs,  and  the  influences  of  the  culti- 
vation of  a  previous  crop  must  be  considered  when  we 
plan  a  rotation. 

The  practice  of  the  proper  systems  of  rotation  makes 
it  possible  to  maintain,  at  low  cost,  the  supply  of  organic 


^^^^^^^^^jJ^^jT^^^ 

Fig.  30. — Field   of   Cowpeas  ready  to   plow    under.     (Farmers'  Bul- 
letin 278,  U.  S.  Dept.  Agr.) 


matter  in  the  soil.  Organic  matter  may  be  supplied  in 
the  form  of  animal  manures,  but  this  source  of  supply 
is  very  limited  when  we  consider  the  total  area  in  culti- 
vation. Some  organic  matter  is  also  accumulated  in  pas- 
tures and  in  woodland,  but  these  methods  of  incorporating 
organic  matter  are  quite  slow.  The  incorporation  of  resi- 
dues from  field  crops,  especially  the  leguminous  crops,  is 
the  best  method  for  increasing  the  amount  of  organic 
matter  in  the  soil. 


SOIL  FORMATION,  COMPOSITION,  ETC. 


85 


TABLE  VI.— THE  CONTENT  IN  PLANT  FOOD  OF  CERTAIN 
AIR-DRIED  LEGUMINOUS  CROPS 


Percentage  Composition. 

Nitrogen  (N). 

Phosphoric 
Acid  (P2O6). 

Potash  (K2O). 

Red  clover,  medium 

Red  clover,  mammoth .... 
Alsike  clover 

2.07 
2.23 
2.34 
2.75 
2.05 
2.19 
2.50 
1.91 
2.80 

0.38 
0.55 
0.67 
0.52 
0.40 
0.51 
0.52 
0.40 
0.75 

2.20 
1.22 
2.23 

White  clover 

1.81 

Crimson  clover 

1  31 

Alfalfa 

Cowpea 

Bean , 

Vetch 

1.68 
1.47 
1.3^ 
2.30 

TABLE  VII.— COMPOSITION  OF  VARIOUS  CROP  RESIDUES 


Percentage  Composition. 


Nitrogen  (N). 


Corn  stalks 

Wheat  straw 

Oat  straw 

Cotton  bolls 

Cotton  leaves 

Cotton  stems 

Cotton  roots 

Cowpea  vines 

Alfalfa 

Soy  bean  straw 

Red  clover,  medium .  .  .  . 
Red  clover,  mammoth .  . 

Alsike  clover 

White  clover 

Crimson  clover 

Pasture  grasses  (mixed) . 

Timothy 

Orchard  grass 

Sorghum 

S.  potato  vines 


0.80 
0.59 
0.62 
1.36 
2.37 
0.83 
0.17 
2.50 
2.19 
1.75 
2.07 
2.23 
2.34 
2.75 
2.05 
0.91 
0.48 
0.43 
0.23 
2.00 


Phosphoric 
Acid  (PiOs). 


0.18 
0.12 
0.20 
0.40 
0.46 
0.22 
0.24 
0.52 
0.51 
0.40 
0.38 
0.55 
0.67 
0.52 
0.40 
0.23 
0.26 
0.16 
0.09 
0.28 


Potash  (KjO). 


1.04 
0.51 
1.24 
2.90 
0.83 
0.92 
0.86 
1.47 
1.68 
1.32 
2.20 
1.22 
2.23 
1.81 
1.31 
0.75 
0.76 
0.76 
0.23 
2.81 


86  CHEMISTRY  OF  FARM  PRACTICE 

Rotation  encourages  diversified  farming,  which,  when 
properly  carried  on^  greatly  aids  in  keeping  the  land  in 
good  condition.  When  the  single -crop  system  is  employed, 
if  that  crop  is  a  clean-cultured  one,  as  is  usually  the  case, 
the  organic  matter  of  the  soil  becomes  depleted,  the  soil 
erodes  more  easily  and,  consequently,  "  gullying  "  sets  in. 
When  land  once  begins  to  wash,  it  is  difficult  to  keep  the 
most  valuable  part  of  the  soil  from  being  lost.  The  top- 
soil  is  the  most  active  in  furnishing  plant  food  and  in  pro- 


Fig.  31. — A  cover  crop  on  corn  land.     (Permission  F.   G.   Tarbox, 
S.  C.  Exp.  Station.) 


moting  plant  growth.  When  this  soil  is  washed  away, 
the  land  becomes  unproductive  and  it  takes  many  years 
of  careful  building  to  restore  it  to  its  former  fertility.  The 
rebuilding  of  soil  is  time-consuming  and  expensive,  there- 
fore care  should  be  exercised  to  prevent  erosion.  Erosion 
may  be  prevented  by  the  incorporation  of  organic  matter, 
deep  plowing,  and,  in  some  cases,  by  terracing. 

66.  Proper  Sequence  of  Crops.     In  arranging  rotations, 
the  endeavor  should  be  to  avoid  having  a  crop  that  feeds 


SOIL  FORMATION,  COMPOSITION,  ETC.  87 

heavily  on  a  particular  element,  followed  by  another  crop 
that  feeds  heavily  on  the  same  element;  nor  is  a  crop 
that  requires  a  large  amount  of  any  particular  element 
adapted  to  a  soil  that  does  not  contain  a  fair  amount  of 
that  element.  Shallow-rooted  crops  should  be  followed 
by  deep-rooted  crops;  clean-cultured  crops  as  much  as 
possible  by  crops  that  will  leave  much  organic  matter  to 
be  incorporated  in  the  soil.  Leguminous  crops  should  be 
used  frequently  in  rotations,  in  order  that  the  largest 
amount  of  the  expensive  element,  nitrogen,  may  be  obtained 
from  the  supply  that  exists  in  the  atmosphere.  It  is  only 
when  a  high-priced  crop  is  being  grown  that  a  farmer 
can  afford  not  to  rotate  his  crops. 

67.  Use  of  Manures.  When  manure  is  intelligently 
conserved,  a  profit  can  be  made  by  feeding  leguminous 
crops  to  stock  and,  while  obtaining  profit  on  the  increase 
in  flesh,  recovering  most  of  the  fertilizing  elements  in  the 
manure,  in  a  better  state  of  mechanical  division  than  it 
was  as  plant  tissue.  It  does  not  follow  necessarily,  however, 
that  the  plant  food  will  be  more  available  in  manure  than 
in  the  plant  tissues.  The  question  for  the  farmer  to  de- 
cide is,  whether  or  not  it  is  more  economical  for  him  to 
feed  the  crops  to  animals,  conserve  the  manure  and  apply 
it  to  his  soil,  or  to  incorporate  the  organic  matter  from 
the  crops  directly  in  the  soil.  Hopkins,  in  his  "  Soil  Fer- 
tility and  Permanent  Agriculture,"  gives  the  table  on 
page  88,  showing  that  a  large  part  of  the  organic  matter 
during  the  processes  of  digestion  and  assimilation  is  decom- 
posed into  carbon  dioxide  and  water,  and  that  little 
over  25  per  cent  of  the  dry  matter  is  recovered  in  the 
manure. 

Doubtless,  the  best  practice  for  the  farmer  to  follow 
will  depend  upon  the  money  value  of  the  crop  that  he 
grows.  If,  for  example,  a  valuable  crop  is  to  be  grown  for 
market,  it  will  pay  to  grow  a  previous  crop  and  incor- 
porate it  in  the  soil,  provided  the  increased  yields  of  sue- 


CHEMISTRY  OF  FARM  PRACTICE 


TABLE    VIII.— THE    AVERAGE    DIGESTIBILITY    OF    SOME 
COMMON   FOOD   STUFFS 


Food  Stuffs. 


Pasture  grasses. ... 
Red  clover,  green. . 
Alfalfa,  green ..... 

Mixed  meadow  hay, 
Red  clover  hay. ... 
Alfalfa  hay 

Oat  straw 

Wheat  straw 

Corn  stover 

Shock  corn , 

Corn-and-cob  meal . 
Corn  ensilage 

Oats 

Corn 

Wheat  bran 


Percent  Digested 

OF  Total  in 

Food. 


Dry 

Matter. 


71 
66 

67 

61 
61 
60 

48 
43 
60 

63 
79 
64 

70 
91 
61 


Nitrogen. 


70 
67 

81 

57 
62 
74 

30 
11 
45 

42 
52 
49 

78 
76 
79 


Dry  Matter  of 

Food:  Recovered 

IN  Manure. 


Percent. 


29 
34 
33 

39 
39 
40 

52 
57 
40 

37 
21 
36 

30 

9 

39 


Pounds 
per  Ton. 


580 
680 
660 

780 
780 
800 

1040 

1140 

800 

740 
420 
720 

600 
180 

780 


ceeding  crops  will  more  than  repay  for  the  value  of  the 
crop  returned  to  the  soil.  If,  on  the  other  hand,  the  crops 
grown  will  not  fulfill  the  above  requirements,  it  will  pay 
to  use  the  plants  for  feed,  and  to  carefully  conserve  the 
manure.  However,  it  has  been  shown  that  there  is  a  con- 
siderable loss  in  organic  matter,  due  to  the  exhalation  of 
carbon  dioxide  by  the  animals  to  which  the  material  is 
fed.  There  is  a  further  loss  of  nitrogen  due  to  the  forma- 
tion of  muscle  and  sinew,  which  contain  a  large  percentage 
of  this  element;  and  of  phosphorus  and  potassium  due  to 
the  formation  of  bone.     From  the  foregoing  statements,  it 


SOIL  FORMATION,  COMPOSITION,  ETC. 


89 


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90  CHEMISTRY  OF  FARM  PRACTICE 

can  readily  be  seen  that  a  young  and  growing  animal  will 
remove  considerably  more  plant  food  and  use  it  in  the 
elaboration  of  tissue  than  will  a  mature  animal.  Another 
factor  influencing  the  composition  of  the  manure  will  be 
the  composition  of  the  feed.  The  third  factor,  which  is 
probably  the  most  important  of  all,  is  the  care  of  the 
manure.  If,  after  carefully  considering  his  own  conditions, 
the  farmer  decides  that  it  is  more  profitable  for  him  to 
feed  the  crop  and  return  the  manure  to  the  land,  which 
is  usually  the  decision  reached  in  diversified  farming,  there 
are  several  factors  still  to  be  considered;  these  will  be 
discussed  in  the  following  chapter. 

68.  Keeping  the  Land  Covered.  Under  the  prevaihng 
methods  of  crop  growth,  the  land  is  allowed  to  lie  bare  a 
part  of  the  year.  During  this  time,  especially  if  the  weather 
is  warm,  there  is  some  nitrification  going  on,  and  much 
plant  food  is  lost  through  leaching.  It  is  good  practice 
to  keep  a  growing  crop  on  the  land  as  much  as  possible, 
to  take  up  the  plant  food  as  it  becomes  available  and  con- 
vert it  into  an  organic  form.  If  such  a  crop  is  planted  as 
a  winter  protection  to  the  soil,  it  is  known  as  a  cover  crop. 
The  cover  crop  is  a  material  aid  in  the  prevention  of 
washing,  because  it  fills  the  soil  with  fibrous  roots  which 
tend  to  hold  the  soil  together.  When  a  crop  is  planted 
between  two  other  crops,  it  is  known  as  a  catch  crop.  An 
example  is  the  planting  of  cowpeas  or  soy  beans  after 
grain  has  been  harvested  and  before  another  grain  crop  is 
planted. 

When  leguminous  plants  can  be  used  for  cover  or  catch 
crops,  or  in  connection  with  other  crops  used  for  this  pur- 
pose, they  serve  another  purpose;  that  of  collecting  nitro- 
gen from  the  atmosphere  and  storing  it  in  such  a  form 
that  it  is  available  as  plant  food.  A  more  general  use  of 
cover  crops  and  catch  crops,  especially  of  the  legumes, 
will  mark  a  great  step  forward  in  our  agricultural  devel- 
opment.    For  cover  crops,   clovers,  vetch,   oats,  and  rye 


SOIL  FORMATION,  COMPOSITION,  ETC.  91 

are  excellent.  For  Southern  conditions,  soy  beans  and 
cowpeas  for  summer  crops,  and  vetch,  oats,  and  rye  for 
winter,  are  most  easily  grown,  though  crimson  clover,  red 
clover,  and  burr  clover  are  excellent  when  established. 
At  the  North,  the  clovers  are  favorites,  because  they  may 
be  included  in  the  regular  rotations. 


CHAPTER  X 
ANIMAL   MANURES 

69.  Quality.  The  quality  of  animal  mamire  depends 
largely  upon  three  factors:  The  composition  of  the  feed,  the 
age  of  the  animal  fed,  and  the  handling  to  which  the  manure 
is  subjected.  The  causes  which  account  for  the  influence  of 
the  age  of  the  animal  have  already  been  discussed  in  Sec. 
67,  and  they  show  the  importance  of  feeding  mature  animals 
as  much  as  practicable,  where  the  composition  of  the  manure 
is  a  consideration.  The  use  of  feeds  rich  in  nitrogen, 
phosphoric  acid,  and  potash,  where  the  price  of  such  feeds 
permits,  produces  the  most  valuable  manures.  Cottonseed 
meal,  a  feed  rich  in  the  elements  named,  sells  for  a  reasonable 
price,  and  can  be  fed  in  moderation  to  advantage  to  all 
farm  animals  except  hogs.  It  is  the  cheapest  source  of 
protein  on  the  market.  In  buying  feeds  and  in  com- 
pounding rations,  the  plant  food  content  of  the  feed  should 
receive  consideration. 

70.  Liquid  Manures.  It  is  very  important  that  an  abun- 
dant supply  of  absorbent  litter  be  used  in  the  stables,  to 
take  up  the  liquid  manure.  It  is  best  to  use  a  litter  that 
readily  nitrifies  and  that  carries  as  high  per  cent  of  plant 
food  as  possible.  Table  IX  gives  the  compositions  of  some 
materials  suitable  for  bedding.  Some  of  the  materials,  corn 
stalks  for  example,  should  be  shredded  before  being  used. 

Table  X  emphasizes  the  fact  that  most  of  the  nitrogen  and 
potash  is  voided  in  the  liquid  manure,  and  it  further  shows 
that  an  abundant  supply  of  absorbent  litter  should  be  used 
to  conserve  properly  the  liquid  manure.  The  manure  fur- 
nishes an  excellent  medium  for  bacteria,  and,  consequently, 
hastens  the  availability  of  the  plant  food  in  the  litter. 

92 


ANIMAL  MANURES 


93 


TABLE   IX.— MATERIALS  SUITABLE   FOR  BEDDING 


Corn  stalks 

Wheat  straw 

Oat  straw 

Rye  straw 

Marsh  haj' 

Sweet  potato  vines .  . 

Cotton  bolls 

Cotton  leaves 

Cotton  steins 

Long-leaf  pine  straw 
Short -leaf  pine  straw 


Phos.  Acid, 
Per  Cent. 


0.30 
0.12 
0.20 

0.28 
0.36 
0.28 
0.40 
0.46 
0.22 
0.24 
0.15 


TABLE  X.— THE  CONTENT  OF  PLANT  FOOD  PRESENT  IN 
SOLID  AND  LIQUID  MANURE,  ACCORDING  TO  VIVIAN 


Nitrogen, 
Per  Cent. 

Phosphoric  Acid, 
Per  Cent. 

Soda  and  Potash, 
Per  Cent. 

Solid. 

Liquid. 

Solid. 

Liquid. 

Solid. 

Liquid. 

Horses 

0.50 

1.20 

0.35 

trace 

0.30 

1.50 

Cows 

0.30 

0.80 

0.25 

trace 

0.10 

1.40 

Swine 

0.60 

0.30 

0.45 

0.125 

0.50 

0.20 

Sheep 

0.75 

1.40 

0.60 

0.05 

0.30 

2.00 

TABLE  XL— NITROGEN,  PHOSPHORIC  ACID  AND  POTASH 
PRESENT  IN   ROTTED   MANURES 


Per  Cent 

Phos.  Acid 

(PiOs). 

Per  Cent 
Nitrogen 

(N). 

Per  Cent 
Potash 
(K2O). 

Horse  manure,  rotted 

0.40 

0.50 

0.50 

Cow  manure,  rotted 

0.30 

0.50 

0.45 

Sheep  manure,  rotted 

0.80 

0.65 

0.60 

Hog  manure,  rotted 

0.80 

0.60 

0.30 

Hen  manure 

0.25 

1.30 

0.20 

94 


CHEMISTRY  OF  FARM  PRACTICE 


71.  Rotted    Manures.     Table    XI    shows    that    rotted 
sheep  manure  has  a  higher  nitrogen  content  than  any  ether 


a 


rotted  manure,  and  next  to  this  comes  hog  manure.     The 
nitrogen  content  of  horse  and  of  cow  manure  when  rotted 


ANIMAL  MANURES  95 

is  nearly  the  same.  The  horse  and  the  cow  manure  contain 
more  potash  than  the  manure  from  hogs.  On  the  other 
hand  sheep  and  hog  manures  run  higher  in  phosphoric 
acid.  An  explanation  of  this  can  probably  be  found  in 
the  fact  that  the  horse  cjid  the  cow  largely  make  use  of 
different  sources  of  feed  than  those  consumed  by  hogs  and 
sheep. 

Horse  manure  ferments  very  rapidly  under  certain 
conditions,  and  the  best  method  for  the  farmer  to  pursue 
is  to  haul  the  manure  to  the  field  frequently  and  apply  it 
to  a  growing  crop;  but  such  method  is  often  impracticable, 
du3  to  the  extra  labor  entailed,  inclemency  of  the  weather, 
and  the  fact  that  there  is  not  always  a  growing  crop  avail- 
abb.  Where  horse  manure  is  kept  in  a  pile  for  some  time, 
it  must  be  packed  down  sufficiently  to  prevent  violent 
nitrification,  followed  by  denitrification,  which  is  known 
as  firefanging.  This  latter  condition  results  in  the  loss  of 
much  of  the  nitrogen,  and  the  material  is  just  as  truly  ashed 
in  the  firefanged  spots  as  though  it  had  been  in  the  fire. 
When  manures  firefang,  they  heat  and  Uberate  gases  both 
injurious  and  uncomfortable  to  the  animals.  There  is 
little  danger  of  firefanging  of  cow  manure  because  this 
manure  will  not  heat. 

72.  Effect  of  Exposure  to  the  Weather.  In  handling 
dairy  cattle,  it  is  absolutely  necessary  that  the  stalls  be 
kept  scrupulously  clean.  In  such  a  case  it  may  be  advis- 
able that  the  manure  be  hauled  out  every  day,  if  possible, 
and  spread  upon  the  land  that  has,  or  is  soon  to  have,  a 
growing  crop.  Preferably  the  manure  should  be  plowed 
in  as  soon  as  possible.  It  has  been  shown  at  the  Maryland 
Experiment  Station  that,  when  80  tons  of  manure  were 
exposed  to  the  weather  for  a  period  of  one  year,  the  weight 
was  reduced  to  27  tons.  At  the  Experiment  Station  of 
the  Dominion  of  Canada,  when  2  tons  of  manure,  con- 
taining 1938  pounds  of  dry  matter,  were  exposed  for  four 
summer  months,  the  dry  matter  was  reduced  to  655  pounds 


96  CHEMISTRY  OF  FARM  PRACTICE 

through  the  agencies  of  fermentation  and  decay.  During 
the  same  time,  the  nitrogen  content  was  reduced  from  48.1 
pounds  to  27.7  pounds.  These  experiments,  as  well  as 
many  more  that  could  be  cited,  show  the  importance  of 
applying  the  manure  and  incorporating  it  into  the  soil 
as  soon  as  possible. 

73.  Rate  of  Application.  The  rate  of  application  of 
animal  manures  should  vary  considerably.  It  depends 
upon  two  factors:  The  supply  of  manure  and  the  section 
of  the  country.  The  reason  that  the  supply  is  a  factor, 
is  that  manure  is  a  good  medium  for  the  growth  of  bacteria, 
in  addition  to  the  plant  food  content;  therefore  it  should 
be  spread  over  as  much  land  as  practicable  to  furnish 
bacteria  flora  to  the  soil.  Conditions  affecting  nitrification 
differ  in  various  sections  of  the  country.  Thus  the  con- 
ditions prevalent  in  the  southeastern  part  of  the  United 
States  favor  rapid  nitrification;  in  fact,  very  noticeable 
results  have  been  obtained  in  South  Carolina  from  the 
use  of  only  2  tons  of  manure  per  acre,  applied  to  cotton. 
On  the  other  hand,  the  conditions  existing  further  north 
favor  slower  nitrification;  consequently,  heavier  applica- 
tions are  necessary,  but  heavy  applications  under  these 
conditions  are  more  lasting  in  their  influence.  For  general 
farm  crops  in  the  South,  it  is  advisable  to  apply  about  6 
tons  of  manure  per  acre,  while  in  some  Northern  sections  of 
the  United  States,  from  12  to  20  ton  applications  frequently 
are  made. 


CHAPTER  XI  , 

AGRICULTURAL  LIME 

74.  Sources  of  Lime.  Lime  is  found  in  limestone 
(mainly  CaCOs)  which  is  widely  distributed  over  the  United 
States,  principally  as  calcite,  dolomite,  marl,  chalk,  and 
deposits  of  the  shells  of  mollusks  or  other  marine  animals. 
Limestone,  when  burned,  yields  calcium  oxide,  called  quick 
lime,  which,  when  slaked  with  water  and  mixed  with  sand, 
is  made  into  mortar.  Dolomite  is  rock  composed  mainly 
of  the  carbonates  of  calcium  and  magnesium.  Marl  con- 
sists of  calcium  carbonate  mixed  with  clay,  or  peat  in 
varying  proportions.  Its  calcium  carbonate  content  ranges 
from  5  to  90  per  cent. 

75.  Effects  of  Lime  on  the  Soil.  Lime  is  beneficial  to 
the  soil  on  account  of  its  chemical,  physical,  and  biological 
effects.  Lime  also  acts  as  a  direct  plant  food ;  for  cal- 
cium is  one  of  the  ten  elements  necessary  for  plant  growth, 
although  it  is  used  by  plants  in  less  amount  than  is  potas- 
sium or  magnesium.  Any  of  the  soluble  salts  of  calcium 
may  serve  to  furnish  the  element  calcium  for  plant  food. 
However,  only  three  forms — calcium  oxide  (quick  lime), 
calcium  hydroxide  (slaked  Ume),  and  calcium  carbonate 
(limestone) — serve  to  correct  acidity  of  the  soil.  The  cor- 
rection of  acidity  has  an  important  influence  on  the  devel- 
opment of  the  bacterial  flora,  and  it  also  assists  nitrification 
by  furnishing  a  basic  material  to  combine  with  the  nitric 
acid  which  is  formed  when  the  nitrogen  of  the  air  becomes 
"  fixed  "  or  oxidized. 

The  different  compounds  of  calcium  vary  in  their  chem- 
ical action  upon  soil.  Calcium  oxide,  or  quick  lime,  being 
a  caustic,  is  very  active  chemically.     It  decomposes  organic 

97 


98  CHEMISTRY  OF  FARM  PRACTICE 

matter,  corrects  acidity,  furnishes  the  element  calcium, 
and  by  means  of  its  chemical  activity  reacts  with  other 
bases  in  the  soil.  An  example  of  this  last  effect  is  found 
in  the  reaction  between  lime  and  the  zeolites  of  the  soil, 
which  are  the  double  silicates  of  aluminium  and  some  other 
base,  the  base  being  changed  by  substitution  of  calcium 
due  to  the  action  of  lime.  In  this  way,  lime  may  serve  to 
liberate  potassium,  which  must  be  present  in  available  form 
in  a  fertile  soil.  Lime  may  also  bring  about  reactions  with 
the  phosphates  of  iron  or  aluminium,  the  product  being 
a  phosphate  of  lime,  which  is  more  soluble  and  therefore 
more  available  for  plant  food  than  the  phosphates  of  iron 
or  aluminium. 

Calcium  hydroxide  is  produced  by  the  action  of  water 
upon  quicklime  and  is  similar  in  its  action  to  calcium 
oxide.  When  applied  to  the  soil,  calcium  oxide  is  quickly 
converted  into  calcium  hydroxide  by  moisture 

CaO+H20  =  Ca(OH)2, 

which,  in  turn,  is  rapidly  converted  by  the  carbon  dioxide 
of  the  air  into  calcium  carbonate 

Ca(OH)2+C02  =  CaC03+H20. 

Calcium  carbonate  is  not  caustic,  and  consequently  it  is 
much  less  drastic  in  its  effects  than  is  the  oxide  or  hydroxide. 
Carbonates  are  easily  decomposed  by  acids,  therefore  the 
application  of  ground  limestone  serves  to  correct  acidity 
in  soils.  In  humid  regions  probably  it  is  rapidly  converted 
into  calcium  silicate.  Calcium  carbonate  fulfills  most  of 
the  functions  performed  by  calcium  oxide  and  calcium 
hydroxide,  but  it  acts  in  a  much  milder  manner.  Calcium 
silicate  (CaSiOs)  and  calcium  sulphate  (Ca2S04)  or  "  land 
plaster,"  serve  most  of  the  functions  of  the  other  forms 
of  lime  except  the  correction  of  acidity,  the  effectiveness 
of  the  salts  varying  with  their  solubilities. 

Lime  modifies  the  physical  structure  of  soils.     It  tends 


AGRICULTURAL  LIME 


99 


to  flocculate  clay,  permitting  a  freer  circulation  of  capil- 
lary water.  It  also  serves  to  bind  together  sandy  soils, 
making  them  more  compact.  The  action  of  caustic  lime 
on  muck  or  peat  soils  is  usually  very  beneficial:  first,  because 


Fig.  34. — Burning  lime  on  the  farm.  Details  of  construction  of  a  farm 
limekiln,  a,  Cross-section,  showing  layers  of  rock  and  coal;  6, 
longitudinal  section,  showing  side  hill  used  as  back  wall;  c,  ground 
plan,  showing  trench  and  grate;  d,  completed  kiln,  walled  in  and 
plastered  with  mud.     (Farmers'  Bulletin  435,  U.  S.  Dept.  Agr.) 


it  brings  about  the  rapid  destruction  of  organic  matter, 
accompanied  by  the  liberation  of  considerable  amounts  of 
soluble  plant  food;  second,  because  it  promotes  the  decom- 
position of  the  excess  of  organic  matter,  resulting  in  improved 
structure  of  the  soil.     When  caustic  lime  is  applied,  there 


100  CHEMISTRY  OF  FARM  PRACTICE 

is  danger  of  depleting  the  organic  matter  in  soils  which 
are  not  well  supplied  with  it,  but  this  does  not  hold  true 
for  applications  of  calcium  carbonate.  In  soils  moderately 
well  supplied  with  organic  matter,  the  use  of  heavy  appli- 
cations of  caustic  lime  may  lead  to  the  Uberation  of  more 
available  nitrogen  than  the  plants  can  use.  In  this  case 
some  plant  food,  especially  nitrogen,  will  be  lost.  Exces- 
sive applications  of  caustic  Ume,  even  to  clay  soils,  may 
lead  to  the  fiocculation  of  the  clay  to  such  an  extent  that 
percolation  will  be  too  rapid.  The  flocculating  power  of 
lime  may  be  illustrated  by  adding  lime  water  or  milk  of 
lime  to  water  containing  clay  in  suspension,  when  it  will 
be  observed  that  the  clay  particles  rapidly  settle  out. 

Caustic  lime,  when  applied  excessively,  may  exert  a 
harmful  effect  on  the  soil  bacteria,  and  temporarily  arrest 
to  some  extent  the  useful  functions  performed  by  these 
agents;  but  this  form  of  lime,  when  applied  in  moderate 
amounts,  is  usually  quickly  changed  to  a  neutral  salt, 
either  calcium  carbonate  or  calcium  silicate.  The  former 
salt  is  still  effective  to  correct  acidity,  but  calcium  silicate 
does  not  exert  such  an  influence. 

The  fact  that  continuous  liming  without  manure  makes 
land  less  productive  than  it  formerly  was,  has  led  many 
people  to  object  to  the  use  of  lime  altogether.  The  initial 
application  of  lime  produces  such  marked  results,  due  to 
its  influence  on  the  stored  plant  food  in  the  soil,  that  the 
fact  that  its  effects  are  indirect  is  not  recognized  and  there 
is  a  temptation  to  continue  its  use  at  the  expense  of  the 
potential  fertility  of  the  soil.  It  is  very  unusual  for  the 
soil  to  contain  such  an  insufficient  supply  of  lime  that 
lack  of  calcium  becomes  a  limiting  factor  in  plant  growth. 

76.  Shipping  Lime.  The  main  forms  of  lime  marketed 
for  agricultural  purposes  are  "  quick  lime  "  (CaO),  "  water- 
slaked  lime  "  (Ca(0H)2)  and  "  air-slaked  lime  "  (CaCOs). 
To  ship  agricultural  lime  a  long  distance  involves  large 
expense^   due  to  freight  charges.     A  ton  of  water-slaked 


AGRICULTURAL  LIME 


101 


lime,  or  calcium  hydroxide,  contains  only  1513  pounds  of 
calcium  oxide,  the  remaining  487  pounds  consisting  of 
water,  and  a  ton  of  air-slaked  lime,  or  calcium  carbonate, 
contains  only  1120  pounds  of  calcium  oxide,  the  remaining 
880  pounds  being  composed  of  carbon  dioxide,  while  quick- 
lime should  be  pure  calcium  oxide.  On  this  basis  of  com- 
parison, we  see  that  it  is  much  more  expensive  to  freight 
a  given  amount  of  calcium  in  the  carbonate  or  hydroxide 
form  than  in  the  oxide  form.  In  shipping,  it  is  necessary 
that  the  quicklime  and  water-slaked  lime  be  barreled  or 
sacked,  because  by  exposure  to  moisture  and  air  both  of 
these  materials  are  transformed  into  air-slaked  lime,  and 
also  on  account  of  the  difficulty  of  loading  and  unloading 
these  caustic  materials.  The  air-slaked  lime,  or  ground 
limestone  rock,  which  are  each  calcium  carbonate,  and 
not  caustic,  may  be  handled  without  containers. 

The  same  condition  holds  for  hauling  the  different 
forms  of  lime  from  the  railroad  station  to  the  farm  that 
held  in  the  freight  charges.  It  is  most  economical  to  haul 
the  quicklime,  the  water-slaked  costing  somewhat  more, 
and  the  carbonate  of  lime  is  most  expensive  for  cartage, 
though  the  carbonate  is  the  most  easily  handled.  A  smaller 
application  of  caustic  lime  will  produce  more  marked 
effects  than  will  a  larger  applicaticn  of  carbonate  of  lime, 
although  the  latter  is  more  lasting  in  its  influences.  The 
amounts  of  other  forms  of  lime  which  are  equivalent  to  a 
ton  of  quicklime  are  given  in  Table  XII. 


TABLE  XII 


Quicklime, 
Pounds. 

Water-slaked 
Lime,  Pounds. 

Air-slaked 
Lime,  Pounds. 

2000 

2643 

3571 

77.  Applying  Lime  to  the  Soil.     Some  difficulty  attends 
the  distribution  of  quicklime  on  the  soil,  for  it  is  necessary 


102 


CHEMISTRY  OF  FARM  PRACTICE 


to  slake  it  before  it  can  be  spread.  This  is  often  accom- 
plished by  putting  the  material  in  small  piles  at  regular 
intervals  over  the  field  and  covering  the  piles  with  moist 
earth,   which   promptly   water-slakes   the   lime,   making  it 


Fig.  35. — Effect  of  liming  spinach.     (R.  I.  Exp.  Station.) 


into  a  powdered  condition  in  which  it  may  easily  be  spread 
from  the  piles. 

A  number  of  State  Experiment  Stations  have  investi- 
gated the  use  of  lime,  in  various  forms,  with  the  general 
conclusion  that  best  results  are  obtained  from  the  use  of 
calcium  carbonate.  Results  at  the  Pennsylvania  Station, 
covering  a  period  of  over  sixteen  years,  indicate  that  on 


AGRICULTURAL  LIME 


103 


plots  to  which  caustic  Ume  (Ca(0H)2)  was  applied  as  com- 
pared with  the  application  of  twice  the  quantity  of  ground 
limestone  (CaCOa)  there  was  a  loss  from  the  caustic  lime, 
during  that  period,  of  375  pounds  of  nitrogen,  without  a 
corresponding  increase  in  yield. 

At  the  Rhode  Island  Station,  it  was  found  that  Ken- 
tucky blue  grass,  timothy,  awnless  brome  grass,  meadow 
oat  grass,   tall  fescue,   and  orchard  grass  were  benefited. 


Fig.   36. — Distributing   lime   with   a   lime   spreader.     (Bulletin    159, 
Ohio  Exp.  Station.) 


while  red  top  and  Rhode  Island  bent  did  well  without  lime. 
Beets  and  spinach  showed  marked  effects  from  liming,  less 
marked  effects  being  shown  on  rye,  carrots,  and  crimson 
clover.  The  following  plants  were  improved,  due  to  appli- 
cation of  lime:  Strawberries,  asparagus,  rhubarb,  white 
mustard,  leeks,  endive,  mangel  wurzels,  muskmelons,  dwarf 
brown  corn,  sweet  peas,  and  poppies.  Watermelons  are 
greatly  injured  by  applications  of  lime,  and  should  not  be 
planted  on  limed  soil  until  three  or  four  years  have  elapsed 


104  CHEMISTRY  OF  FARM  PRACTICE 

since  the  application.  Parsley  and  chicory  show  little 
benefits  from  liming. 

It  is  advisable  to  apply  lime  in  autumn,  preferably  after 
a  large  amoimt  of  vegetable  material  has  been  turned 
under.  The  lime  may  be  applied  by  means  of  machines 
especially  constructed  for  the  purpose,  and  should  be 
spread  as  evenly  over  the  surface  of  the  soil  as  possible, 
and  disk-harrowed  in  to  the  depth  of  about  two  inches. 

78.  Machine  for  Applying  Lime.  The  Ohio  Station 
makes  the  following  recommendation  for  constructing  a 
home-made  machine  for  the  appUcation  of  ground  lime- 
stone. 

Make  a  hopper  similar  to  that  of  an  ordinary  grain  drill,  measur- 
ing inside  8j  feet  or  11  feet  long  with  sides  about  21  inches  wide  and 
about  20  inches  apart  at  the  top.  The  sides  may  be  trussed  with 
f-inch  iron  rods  running  from  the  bottom  at  the  middle  to  the  top 
at  the  ends  of  the  hopper.  Let  the  bottom  be  5  inches  wide  in  the 
clear,  and  cut  in  it  crosswise  a  row  of  diamond-shaped  holes,  2  inches 
wide,  2 1  inches  long,  and  4  inches  apart  (6  inches  between  centers). 
Make  a  second  bottom  with  holes  in  it  of  the  same  size  and  shape 
as  those  of  the  main  bottom,  and  so  shaped  that  they  will  register. 
Let  this  second  bottom  shde  loosely  imder  the  first,  moving  upon 
supports  made  by  leaving  a  space  for  it  above  bands  of  strap  iron 
12  inches  apart,  which  should  be  carried  from  one  side  to  the  other 
under  the  hopper  to  strengthen  it.  The  upper  bottom  piece  may  be 
made  of  about  8-inch  sheet  steel,  and  the  lower  one  may  be  smooth, 
seasoned  hard  wood,  about  1  inch  thick  and  7  inches  wide,  reinforced 
with  strap  iron  if  necessary,  and  well  oiled  or  painted.  To  this  under 
strip  attach  a  V-shaped  arm,  extending  an  inch  in  front  of  the  hopper, 
with  a  half-inch  hole  in  the  point  of  the  V,  in  which  drop  the  end 
of  a  strong  lever,  bolting  the  lever  loosely  but  securely  to  the  side 
of  the  hopper,  and  fasten  to  the  top  of  the  hopper  a  guide  of  strap 
iron,  in  which  the  lever  may  move  freely  back  and  forth.  The  object 
of  this  lever  is  to  regulate  the  size  of  the  openings  by  moving  the 
bottom  board.  Make  a  frame  for  the  hopper,  with  a  tongue  to  it, 
similar  to  the  frame  of  an  ordinary  grain  drill. 

Get  a  pair  of  old  mowing-machine  wheels  with  strong  ratchets 
in  the  hubs,  and  with  pieces  of  round  axle  of  sufficient  length  to  pass 
through  the  frame  and  into  the  ends  of  the  hopper,  which  are  to  be 
welded  to  a  square  bar  of  iron  about  If  inches  in  diameter  and  the 


AGRICULTURAL  LIME  105 

length  of  the  inside  of  the  hopper.  The  axles  should  be  fitted  with 
journals,  bolted  to  the  under  side  of  the  frame. 

Make  a  reel  to  work  inside  of  the  hopper  by  securing  to  the  axle, 
12  inches  apart,  short  arms  of  f-inch  by  1-inch  iron,  and  fastening 
to  these  arms  four  beaters  of  |-inch  square  iron,  about  an  inch  shorter 
than  the  inside  of  the  hopper,  the  reel  being  so  adjusted  that  the 
beaters  will  almost  scrape  the  bottom  of  the  hopper,  but  will  revolve 
freely  between  the  sides.  The  arms  may  be  made  of  two  pairs  of 
pieces,  bent  so  as  to  fit  around  the  axle  on  opposite  sides,  and  secured 
by  small  bolts  passing  through  the  ends  and  through  the  beater, 
which  is  held  between  them.  The  diameter  of  the  completed  reel 
is  about  5  inches,  and  it  serves  as  a  force  feed. 

Two  pieces  of  oilcloth  may  be  tacked  to  the  bottom  of  the  hopper, 
one  in  front  and  one  behind,  of  sufficient  width  to  reach  nearly  to  the 
ground,  in  order  to  reduce  the  annoyance  of  the  flying  dust  to  man 
and  team.  Another  piece  may  be  buttoned  across  the  top  of  the 
hopper  in  windy  weather,  if  desired;  but  the  dust  of  hmestone  or  of 
natural  phosphate  is  certainly  no  worse  than  the  dust  of  the  field. 

A  sort  of  second  force  feed  has  been  evolved  from  the  extensive 
experience  of  Illinois  farmers  in  building  home-made  machines:  Two 
pieces  of  sheet  steel,  each  about  6  inches  wide  and  the  length  of  the 
machine,  are  used  as  a  V-shaped  bottom  for  the  hopper,  forming  nearly 
a  right  angle  at  the  lowest  point.  One  piece  is  stationary  and  the 
other  is  given  an  endwise  motion  back  and  forth  by  means  of  a  small 
wheel  with  a  heavy  rim  waving  in  and  out  horizontally  and  running 
through  a  slotted  piece  firmly  attached  to  the  movable  sheet  steel. 
Two  very  small  wheels  forming  the  sides  of  the  slot  serve  to  reduce 
the  friction,  and  a  lever  is  arranged  to  throw  this  mechanism  out  of 
gear.  One  of  the  pieces  of  sheet  steel  is  provided  with  an  adjustment 
by  means  of  which  a  crack  is  opened  of  any  desired  width,  the  entire 
length  of  the  bottom.  Thus  the  stone  falls,  not  through  holes  or 
in  streaks,  but  in  a  perfect  broadcast.  Several  of  these  home- made 
machines  are  in  use.  The  draft  is  more  than  with  the  reel  alone,  but 
they  are  undoubtedly  more  satisfactory  than  anything  on  the  market. 

The  cash  expense  for  such  a  machine,  aside  from  the 
mower  wheels  with  axle  and  ratchets,  has  varied  from 
less  than  $10  to  more  than  S20,  depending  on  the  cost  of 
material  and  labor.  Farmers  with  some  mechanical  skill 
hire  only  the  necessary  blacksmithing. 

79.  Gypsum.  Many  soils,  especially  in  the  Southeastern 
part  of  the  United  States,  have  received  by  the  applica- 


106  CHEMISTRY  OF  FARM  PRACTICE 

tion  of  superphosphate  fertiUzer,  a  large  quantity  of  gypsum 
(calcium  sulphate).  To  make  superphosphate,  the  ground 
phosphate  rock  is  treated  with  sulphuric  acid,  the  result 
of  this  action  being  a  soluble  calcium  acid  phosphate  and 
gypsum  in  the  proportion  shown  by  the  equation, 

Ca3(P04)2+2H2S04+5H20  = 

2CaS04  •  2H20+CaH4(P04)2  •  H2O. 

Rock  phosphate  contains  other  calcium  salts  than  phos- 
phate, such  as  the  fluoride  and  carbonate,  and  these  also 
appear  as  calcium  sulphate  after  the  action  of  the  sul- 
phuric acid.  Considerably  over  one-half,  often  70  per  cent, 
of  superphosphate  is  gypsum.  This,  however,  is  no  dis- 
advantage, for  gypsum,  when  applied  to  leguminous  crops 
for  the  calcium  sulphate,  releases  potassium  present  in 
an  insoluble  condition  in  clay  soils  formed  by  the  decom- 
position of  feldspar  rocks. 


CHAPTER  XII 

PHOSPHORUS 

80.  Presence  in  the  Soil.  Of  all  minerals  necessary 
for  plant  growth  the  compounds  containing  phosphorus 
are  most  liable  to  be  deficient.  The  average  of  many  anal- 
yses of  the  earth's  crust  shows  the  presence  of  only  yfo 
of  1  per  cent  of  phosphorus,  while  many  of  our  best  arable 
soils  contain  considerably  less  than  that  amount.  The 
phosphorus  present  in  the  soil  is  usually  in  the  form  of  a 
calcium  phosphate.  Calcium,  with  its  valence  of  two,  and 
the  phosphate  radical,  with  its  valence  of  three,  unite  in 
accordance  with  the  criss-cross  rule  stated  previously,  so 
as  to  form  normal  calcium  phosphate  with  the  formula 
Ca3(PO)2.  This  is  known  in  the  trade  as  rock  or  bone 
phosphate.  There  are  also  two  acid  phosphates,  the  di- 
calcium  phosphate  Ca2H2(P04)2,  known  as  reverted  phos- 
phoric acid,  and  the  mono-calcium  phosphate,  CaH4(P04)2, 
which,  when  mixed  with  calcium  sulphate,  is  known  as 
the  superphosphate  of  lime.  The  reaction  with  sulphuric 
acid  by  which  the  insoluble  rock  phosphate  is  converted 
into  the  soluble  superphosphate  is  as  follows: 

Cas  (P04)2 + 2H2SO4  =  CaH4  (P04)2 + 2CaS04. 

Should  there  not  be  enough  sulphuric  acid  to  complete 
this  reaction,  or,  in  other  words,  should  there  be  excess  of 
rock  phosphate,  the  following  reaction  may  take  place : 

CaH4(P04)2+Ca3(P04)2  =  2Ca2H2(P04)2. 

Thus,  there  will  be  formed  the  reverted  phosphate,  which 
is  insoluble  in  water. 

107 


108  CHEMISTRY  OF  FARM  PRACTICE 

The  inorganic  phosphorus  present  in  the  soil  is  generally 
in  the  form  of  the  normal  calcium  phosphate  combined 
with  fluorine  and  chlorine  (Ca3(P04)2CaFCl),  although 
some  of  it  is  found  as  the  phosphates  of  iron  or  aluminium. 
Aluminium  phosphate  is  a  normal  constituent  of  rock  phos 
phate,  but  phosphates  containing  iron,  even  in  very  small 
amounts,  are  rejected,  as  the  iron  has  the  power  in  the  soil, 
even  after  the  treatment  with  sulphuric  acid,  to  take  away 
phosphoric  acid  from  acid  phosphates  and  render  them 
insoluble.  A  small  amount  of  the  total  phosphorus  of  the 
soil  is  found  combined  in  organic  compounds  and  is  Uberated 
by  the  decay  of  organic  matter. 

Experimental  results  have  indicated  that  1  per  cent 
of  the  total  phosphorus  present  in  the  soil  is  available 
during  the  course  of  a  year.  Obviously  this  availability 
will  depend  upon  several  factors,  the  form  of  combination 
of  the  phosphorus,  the  amount  of  soil  moisture,  the  content 
of  decaying  organic  matter,  and  the  influence  of  added 
fertilizers  on  the  solubility  of  the  material  present.  It 
must  be  kept  in  mind  that,  in  explanation  of  the  low  phos- 
phorus content  of  normal  soils,  a  large  per  cent  of  the 
phosphorus  used  is  stored  in  the  seed  of  the  plant,  which 
is  generally  the  product  sold  off  the  farm.  Assuming 
1-^  of  one  per  cent  of  phosphorus  and  2,000,000  pounds  of 
soil  in  the  surface  area  per  acre,  a  total  of  only  1000  pounds 
of  phosphorus  will  be  present,  of  which  perhaps  1  per 
cent  will  become  available,  furnishing  10  pounds  of  phos- 
phorus combined  in  soluble  compounds.  Ten  pounds  of 
soluble  phosphorus,  providing  that  none  leached  out,  would 
furnish  per  acre  phosphorus  sufficient  to  make  43  bushels 
of  corn,  or  62  bushels  of  oats,  or  31  bushels  of  wheat,  or 
cotton  sufficient  to  amount  to  375  pounds  of  lint.  As 
a  matter  of  fact,  many  soils  do  not  contain  as  much  as 
yf  XT  of  1  per  cent  of  phosphorus,  and  some  of  the  available 
phosphorus  is  lost  through  leaching. 

81.  Commercial  Sources.    The  farmer  has  at  his  dis- 


PHOSPHORUS 


109 


a 
-a 
a, 

m 

o 


-a 


3 

-•J 


CO 


110  CHEMISTRY  OF  FARM  PRACTICE 

posal  a  number  of  phosphorus-bearing  materials  to  supply 
a  deficiency  of  phosphorus  in  the  soil.  The  materials  de- 
rived from  farm  lands  are  animal  manures,  bones,  and  some 
vegetable  products,  such  as  cottonseed  meal,  which,  while 
valued  mainly  for  its  nitrogen,  contains  a  considerable 
amount  of  phosphorus.  But  the  phosphorus  in  these  ma- 
terials all  came  originally  from  the  soil;  so,  by  merely 
returning  it,  we  cannot  hope  to  keep  up  the  normal  supply. 
Animal  manures  do  not  contain  enough  phosphorus  to 
make  them  a  balanced  fertilizer,  hence  it  is  desirable  to 
add  a  certain  amount  of  a  phosphatic  fertilizer.  The 
same  is  true  for  cottonseed  meal,  rapeseed  meal,  and  castor 
pomace,  all  of  vegetable  origin,  when  used  in  fertilizer. 
The  most  important  commercial  sources  of  phosphorus 
whereby  the  normal  content  of  the  soil  may  be  main- 
tained are  phosphate  rock,  superphosphate,  bone,  Thomas 
slag,  mineral  phosphate,  and  guano. 

82.  Phosphate  Rock.  This  is  obtained  from  mineral 
deposits  in  the  earth  that  are  directly  traceable  to  organic 
origin.  The  United  States  fortunately  has  large  deposits 
of  this  rock.  Those  in  Florida,  Alabama,  South  Carolina, 
Tennessee,  and  Arkansas  have  produced  enormous  quan- 
tities of  the  rock.  There  are  extensive  deposits  in  Idaho, 
Utah  and  Wyoming  which  are  not  yet  developed.  Within 
the  last  decade  considerable  attention  has  been  devoted 
to  the  use  of  finely  ground  phosphate  rock  as  a  source  of 
phosphorus.  Experiments  have  proved  that  this  ground 
rock  may  profitably  be  used  in  connection  with  animal 
manures  or  an  abundant  supply  of  decaying  organic  matter 
derived  from  any  source.  When  ground  phosphate  rock 
is  purchased,  it  should  be  specified  that  90  per  cent  of  the 
material  shall  pass  through  a  sieve  having  100  meshes,  to 
the  linear  inch.  It  has  been  shown  that  when  50  to  100 
pounds  of  these  "  floats  "  are  mixed  with  each  ton  of  ani- 
mal manure,  good  results  follow.  It  is  advisable  to  get 
floats  which  are  ground  from  unburned  rock,  for  the  burn- 


PHOSPHORUS 


111 


03 


13 


a 


73 


112  CHEMISTRY  OF  FARM  PRACTICE 

ing  drives  off  the  combined  water  and  makes  the  material 
less  soluble. 

83.  Acid  Phosphate  or  Superphosphate.  This  is  the 
form  of  phosphorus  most  used  as  a  fertilizer.  The  reaction 
given  on  page  23  by  which  the  insoluble  phosphate  rock 
is  made  soluble  was  discovered  by  Baron  Liebig  and  was 
applied  by  him  to  the  treatment  of  bones.  About  1845, 
Lawes  made  use  of  this  reaction  for  the  treatment  of  the 
newly  discovered  mineral  source  of  phosphorus,  coprolite, 
and  from  this  beginning  the  manufacture  of  phosphates 
has  grown  into  an  immense  industry.  Superphosphate 
should  not  be  mixed  with  rock  phosphate,  lime,  Thomas 
phosphate,  cyanamid,  or  basic  calcium  nitrate,  because  the 
calcium  contained  in  these  materials  would  "  revert  "  the 
acid  salts  of  calcium  phosphate  into  the  insoluble  dical- 
cium  phosphate,  in  this  way  neutralizing  the  advantages 
of  the  acid  treatment.  A  soluble  phosphate,  when  applied  to 
the  soil,  goes  into  solution  in  the  soil  water  and  is  diffused 
throughout  the  soil.  When  it  comes  in  contact  with  a 
basic  material,  it  is  precipitated  in  fine  solid  condition 
on  the  surface  of  the  soil  particles.  In  this  way,  the  added 
phosphate  is  widely  distributed,  and  the  exudation  from 
root  hairs  of  the  plant,  coming  in  contact  with  it,  dissolves 
the  phosphate,  which  then  by  osmosis  is  taken  into  the 
plant  structure. 

Acid  phosphate  applied  together  with  fertilizer  contain- 
ing nitrogen  and  potash  gives  the  best  results,  the  proper 
proportions  for  each  case  varying  with  the  soil  and  the 
crop  to  be  grown.  In  many  cases,  superphosphate,  when 
applied  alone,  is  advantageous,  especially  on  land  well 
supplied  with  organic  matter.  The  fact  that  superphos- 
phate carries  with  it  much  sulphate  of  lime  or  land  plaster 
should  always  be  remembered  in  connection  with  the  use 
of  this  phosphate  as  a  fertilizer.  Land  plaster  has  the 
property  of  aiding  in  the  breaking  down  of  organic  matter 
in  the  soil  and  of  liberating  potash  and  phosphorus  from 


PHOSPHORUS 


113 


114  CHEMISTRY  OF  FARM  PRACTICE 

insoluble  compounds  in  the  soil,  in  this  way  depleting  in 
time  the  local  supply.  Land  plaster  acts  similarly  to 
lime,  in  that  it  may  furnish  calcium,  an  essential  plant 
food  element.  It  also  assists  in  liberating  nitrogen  from 
organic  compounds  and  also  frees  insoluble  potash  and 
phosphorus,  but  it  does  not  correct  acidity. 

84.  Thomas  Phosphate  or  Basic  Slag.  In  the  manu- 
facture of  steel,  various  processes  are  resorted  to  for  the 
purpose  of  removing  the  phosphorus  from  the  pig-iron 
from  which  the  steel  is  manufactured.  Essentially  all 
processes  consist  of  lining  the  furnaces  with  dolomite,  a 
calcium  magnesium  limestone,  before  the  pig-iron  is  put 
in.  The  mass  is  subjected  to  a  high  heat,  and  the  mag- 
nesium limestone  slags  off  the  phosphorus  as  calcium  phos- 
phate, which  rises  to  the  surface.  This  slag  is  drawn  off 
from  the  converter,  cooled,  broken,  finely  ground  and  placed 
on  the  market.  It  is  stated  that  slag  consists  of  trical- 
cium  phosphate  and  calcium  silicate  in  proportions  shown 
by  the  formula  (CaO)5P205Si02.  This  material  may  con- 
tain some  free  lime,  and  more  lime  may  become  soluble 
by  repeated  washings.  Thomas  slag  gives  good  results 
on  sour  lands  that  contain  organic  matter,  on  lands  rich 
in  humus,  and  on  lands  deficient  in  lime.  It  must  not  be 
mixed  with  any  material  containing  salts  of  ammonia — 
for  example,  sulphate  of  ammonia — because  the  free  lime 
will  liberate  the  ammonia  as  a  gas,  which  will  be  lost. 

85.  Bone.  Among  the  sources  of  phosphorus,  both 
raw  and  steamed  bone  have  held  an  important  place. 
Raw  bone  contains  3  to  4  per  cent  of  nitrogen  in  the  form 
of  organic  matter,  and  from  20  to  25  per  cent  of  phos- 
phoric acid.  About  half  of  this  phosphoric  acid  is  avail- 
able, more  becoming  available  as  the  bone  decays.  The 
composition  of  the  bone  varies  with  the  age  of  the  animal, 
the  bones  of  old  animals  usually  containing  more  phos- 
phorus and  less  nitrogen. 

Bones  are  steamed  for  the  purpose  of  removing  the 


PHOSPHORUS 


116 


gelatine  and  glue.  In  this  process,  much  of  the  nitrogenous 
material  is  removed;  but,  as  the  phosphoric  acid  is  not 
removed  to  any  extent,  the  decrease  in  weight  of  the 
bones  caused  by  the  materials  extracted  brings  about  a 
corresponding  increase  of  the  percentage  of  phosphoric 
acid.     The  process  of  extraction  also  removes  the  greases 


Fig.  40. — Corn  grown  without  the  use  of  special  fertilizer. 


and  fats  which  interfere  with  the  decomposition  of  the  raw 
bone  in  the  soil.  Experiments  show  that  steamed  bone 
acts  more  quickly  and  is  more  valuable  as  a  source  of 
phosphorus  than  raw  bone.  Raw  bone  is  especially  prized 
as  a  source  of  phosphorus  and  nitrogen  for  fruit  trees, 
where  a  slowly  available  supply  of  these  elements  is  desired. 
86.  Mineral  Phosphate.  Deposits  of  mineral  phosphates 
which  are  not  derived  directly  from  organic  sources  are 


116 


CHEMISTRY  OF  FARM  PRACTICE 


widely  distributed  in  rocks  of  igneous  origin.  A  typical 
mineral  phosphate  is  apatite,  a  double  phosphate,  and 
fluoride  of  calcium  with  the  formula  Ca3(P04)2-Ca2FPO^. 
Formerly  large  quantities  of  this  mineral  were  imported 


Fig.  41. — Corn  grown  on  the  same  area  and  soil  as  that  of  Fig.  40, 
with  the  addition  of  500  lbs.  acid  phosphate  and  188  lbs.  dried 
blood  per  acre. 


from  Canada  for  manufacture  into  fertilizer.  The  expense 
of  mining  and  transportation  does  not  permit  this  mineral 
to  enter  into  competition  with  rock  phosphate  as  a  fertilizer. 
87.  Guano.  This  material  has  been  a  rich  source  of 
phosphorus  as  well  as  of  nitrogen.     The  standard  Peruvian 


PHOSPHORUS 


117 


guano  contains  nearly  40  per  cent  of  bone  phosphate, 
corresponding  to  about  18  per  cent  of  phosphoric  acid 
(P2O5).  Certain  small,  rocky  islands  of  Peru,  owing  to 
the  abundance  of  fish  found  in  the  waters  of  these  coasts, 
have  been  the  habitat  for  untold  ages  of  enormous  numbers 
of  sea  birds.  Rain  seldom  falls  in  these  regions  and  the 
excrement  (Spanish  Guano)  has  collected  in  thick  deposits. 


Fig.  42. — Com  grown  under  the  same  conditions  as  that  of  Fig.  40, 
but  with  160  lbs.  of  muriate  of  potash  added  per  acre. 


From  one  group  of  these  small  islands,  the  Chincha,  guano 
to  the  value  of  $1,000,000,000  has  been  taken.  As  a  source 
of  phosphorus  guano  is  much  more  expensive  than  is  rock 
phosphate  and  the  supply  is  being  exhausted. 

88.  Purchase  and  Application  of  Phosphorus.  The  selec- 
tion of  the  source  of  phosphorus  to  use  is  largely  an  economic 
problem  to  be  determined  by  the  costs  of  the  materials 
delivered  on  the  farm.     Lower  prices  for  fertilizing  ma- 


118  CHEMISTRY  OF  FARM  PRACTICE 

terials  are  secured  by  buying  them  in  car-load  lots  from 
the  manufacturer  or  wholesaler.  The  author  has  known 
as  great  a  difference  as  60  per  cent  in  cost  between  buying 
in  car-load  lots  from  the  wholesaler  and  in  buying  in  small 
quantities  from  the  retailer. 

Experiments  have  been  conducted  to  determine  which 
source  of  phosphorus  is  most  effective  for  the  different 
crops  on  different  soils,  taking  into  account  the  cost  of 
the  material  carrying  the  phosphorus.  The  results  of  these 
experiments  agree  that  ground  phosphate  rock  is  the  most 
economical  source  of  phosphorus  on  the  market.  It  has 
an  additional  advantage  in  that  its  content  of  phosphorus 
is  higher  than  that  of  any  other  commercial  source,  thus 
enabling  the  purchaser  to  transport  a  large  number  of 
pounds  of  phosphorus  in  a  ton  of  material.  Its  chief 
disadvantage  lies  in  the  fact  that  it  is  the  most  unavail- 
able source  of  commercial  plant  food. 

Ground  phosphate  rock  can  be  used  to  advantage  under 
two  sets  of  conditions: 

(a)  For  sprinkling  in  stalls  or  barnyards  where  animal 
manures  are  accumulating.  This  addition  of  ground  phos- 
phate rock  should  be  made  at  intervals  so  that  it  will  be- 
come thoroughly  incorporated  with  the  manure.  It  is 
advisable  to  add  ground  phosphate  rock  at  the  rate  of 
from  50  to  100  pounds  for  each  ton  of  manure  accumulated, 
the  quantity  within  these  limits  depending  upon  the  total 
amount  of  manure  to  be  applied  per  acre.  If  applications 
of  more  than  12  tons  of  manure  per  acre  are  to  be  made, 
50  pounds  of  ground  phosphate  rock  per  ton  should  suffice; 
if  lighter  applications  of  manure  are  to  be  made,  100  pounds 
per  ton  would  be  preferable.  The  thorough  incorporation 
of  the  finely  ground  phosphate  in  the  animal  manure  will 
subject  a  large  surface  area  of  that  material  to  the  action 
of  the  acids  present  in  the  manure,  causing  some  of  it  to 
be  converted  into  the  more  available  forms.  After  the 
manure  is  applied  to  the  field,  the  processes  of  nitrifica- 


PHOSPHORUS  119 

tion  will  cause  further  reactions  to  take  place  which  grad- 
ually render  the  phosphorus  available. 

(6)  Ground  phosphate  rock  can  be  used  to  advantage 
in  a  rotation  which  assures  an  abundant  supply  of  decay- 
ing organic  matter.  Decaying  organic  matter  is  the  key 
to  profitable  farming;  few  farmers  realize  when  their  soil 
has  an  abundance  of  this  material.  It  is  the  general  opinion 
that  merely  following  a  rotation  will  assure  an  abundance 
of  organic  matter;  as  a  matter  of  fact,  it  is  necessary  that 
large  crops  be  grown  so  that  the  crop  residues  will  be  large. 


CHAPTER  XIII 
NITROGEN 

89.  Importance  of  Nitrogen.  The  need  of  nitrogen  in 
crop  production  cannot  be  over-emphasized.  The  lack  of 
a  plentiful  supply  of  this  element  in  the  organic  form  will 
inevitably  make  land  infertile.  In  the  formation  of  the 
earth's  crust,  the  addition  of  nitrogen  must  have  been 
very  gradual,  the  first  probably  being  due  to  the  oxidation 
of  atmospheric  nitrogen  by  electrical  disturbances.  This 
operation  is  still  effective,  and  oxides  of  nitrogen  and 
ammonia  gas  (NH3)  in  small  amounts  are  washed  down 
by  rain  water.  Nitrogen  from  this  source  must  have 
nourished  the  earliest  forms  of  plant  life,  and  the  organic 
remains  of  these  lower  plant  forms  must  have  supplied  the 
basis  for  our  supply  of  organic  nitrogen  in  the  soil.  Neces- 
sarily the  accumulation  of  this  supply  required  very  long 
periods  of  time. 

When  enough  organic  matter  had  accumulated  to  make 
possible  the  growth  of  legumes,  the  accumulation  of  nitro- 
gen probably  became  much  more  rapid,  as  these  plants 
bear  round  their  roots  nodules  which  are  the  homes  of 
colonies  of  a  species  of  bacterium  that  have  the  power  of 
causing  the  nitrogen  and  oxygen  of  the  air  to  unite,  thereby 
"  fixing "  the  nitrogen.  There  are  to-day  many  wild 
legumes  still  adding  to  the  supply  of  nitrogen  in  an  organic 
form.  Therefore,  the  cultivation  of  domestic  legumes,  such 
as  the  clovers,  cowpeas,  vetches,  alfalfa,  field  peas,  beans, 
lupines,  and  peanuts  cannot  be  urged  too  strongly.  Certain 
sections  of  the  United  States  make  successful  use  of  these 
crops  in  rotation,  to  furnish  their  nitrogen  supply.  For 
specialized    crops,    such    as    cotton,    tobacco,    sugar    cane, 

120 


NITROGEN 


121 


'O 


fe 


122  CHEMISTRY  OF  FARM  PRACTICE 

sugar  beets,  and  truck,  it  is  necessary  to  make  additional 
use  of  nitrogen  derived  from  a  commercial  source.  How- 
ever, it  is  recommended  that  the  annual  legumes  be  used 
as  catch  crops  and  cover  crops  to  supplement  the  arti- 
ficial supply. 

It  is  an  interesting  fact,  established  experimentally  by 
Lipman  of  New  Jersey,  that  a  non-leguminous  crop  grown 
as  a  companion  crop  with  a  legume  may  derive  nitrogen 
from  the  supply  of  atmospheric  nitrogen  fixed  by  th^^ 
legume.  The  experiment  was  conducted  as  follows:  A 
small  glazed  pot  was  placed  in  a  large  pot  to  serve  as  a 
check,  while  a  small  non-glazed  pot  was  placed  in  another 
pot  for  the  determination.  All  pots  were  filled  with  earth 
and  a  legume  was  planted  in  the  outer  pot  in  each  case, 
and  the  non-legume  in  the  inner  pots.  Where  the  non- 
porous  inner  pot  was  used,  the  non-legume  made  much 
poorer  growth  than  where  the  porous  inner  pot  was  used, 
because  the  soluble  nitrogen  could  go  through  the  walls 
of  the  porous  inner  pot  to  serve  to  nourish  the  non-legume. 

90.  Commercial  Nitrogen  Profitable.  After  supplying 
all  nitrogen  that  it  is  practicable  to  secure  by  means  of 
leguminous  crops,  it  is  still  generally  advisable  to  apply 
nitrogen  in  the  commercial  form  to  specialized,  high-priced 
crops.  The  grower  of  early  truck  can  afford  to  purchase 
a  large  amount  of  high-priced  fertilizer  if  it  will  improve 
the  quality,  yield,  and  early  maturity  of  his  product.  The 
same  will  hold  true  to  a  less  extent  with  tobacco,  sugar 
cane,  sugar  beets,  and  cotton. 

91.  Selection  of  Source  of  Nitrogen.  In  purchasing 
nitrogen  in  its  various  forms,  great  care  must  be  taken  in 
the  selection  of  the  source  to  assure  high  agricultural  value. 
As  nitrogen  is  the  highest  priced  element  of  commercial 
fertilizers,  there  are  more  attempts  to  palm  off  an  inferior 
kind  of  nitrogenous  fertilizer  than  in  the  cases  of  phos- 
phorus or  potassium.  It  is  usually  unwise  to  buy  low- 
grade  fertilizers  at  any  price;    the  best  are  cheapest  in 


NITROGEN 


123 


P5 


Q 


124  CHEMISTRY  OF  FARM  PRACTICE 

the  end,  and  the  reduction  in  price  of  the  inferior  sources 
is  usually  not  great. 

The  crop  grown  and  the  character  of  the  soil  should  be 
the  determining  factors  in  the  selection  of  the  sources  of 
nitrogen.  Light  sandy  soils  are  leachy,  and  do  not  easily 
retain  soluble  plant  food,  therefore  it  is  often  advisable 
to  make  use  of  organic  sources  with  such  soils.  Some 
crops  have  to  be  forced  and  require  a  large  amount  of 
rapidly  available  fertilizer;  but  these  crops  are  usually  eo 
valuable  that  the  grower  can  afford  a  certain  amount  of 
loss  through  leaching. 

92.  Inorganic  Sources  of  Nitrogen.  The  sources  of 
nitrogen  may  be  divided  into  two  classes — organic  and 
inorganic.  The  inorganic  sources  of  the  nitrogen  found 
in  commerce  in  large  quantities  are  potassium  nitrate, 
(KNO3),  sodium  nitrate  (NaNOs),  calcium  nitrate  (Ca(N03)2) 
and  sulphate  of  ammonia  ((NH4)2S04).  These  are  all 
easily  soluble  in  water.  The  nitrates  remain  soluble  under 
all  conditions  until  they  are  either  used  as  plant  food, 
leached  out,  or,  as  occurs  under  very  unusual  conditions, 
lost  through  denitrification.  The  nitrates  are  so  soluble 
that  they  may  be  considered  the  most  thoroughly  predi- 
gested  nitrogenous  plant  food  and,  therefore,  are  most 
efficacious  when  applied  to  a  growing  crop  as  a  topdressing. 
Sulphate  of  ammonia  reacts  with  certain  soil  compounds 
which  render  the  ammonium  radical  (NH4)  less  soluble 
in  water  and,  consequently,  more  slowly  available.  This 
reaction  is  supposed  to  take  place  between  the  ammonia 
s£tlts  and  compounds  in  the  soils  called  zeolites.  The  zeolites 
are  double  hydrated  silicates  of  aluminium  with  some 
other  base  which  is  interchangeable.  Examples  of  zeolites 
are  Thomsonite,  CaAl2Si208,  and  natronite,  Na2Al2Si30io. 
The  bases  that  may  be  substituted  in  the  zeolites  are  cal- 
cium, sodium,  potassium,  and  ammonium.  Sodium  will 
displace  calcium  in  the  zeolitic  compounds,  while  potas- 
sium will  displace  sodium  or  calcium,  and  ammonium  will 


NITROGEN 


125 


displace  potassium,  sodium,  or  calcium.  Ammonia  salts 
are  constantly  forming  in  the  soil;  thus  nature  has  fur- 
nished a  means  for  their  conservation  if  the  nitrification 
is  not  rapid  enough  to  take  up  the  ammonia  formed.  The 
fact  that  the  four  basic  materials  enumerated  above  are 


Fig.  45.* — Blasting  a  test  hole  in  caliche  to  obtain  nitrate  of   soda. 


held  in  the   relative   order   of  their  agricultural   value   is 
significant. 

There  is  another  action  which  may  cause  calcium  to 
liberate    sodium,    potassium,    or    ammonium;     sodium    to 

*  Figs.  45-50  are  furnished  by  The  Nitrate  of  Soda  Propaganda, 
WilUam  S   Myers,  Director. 


126 


CHEMISTRY  OF  FARM  PRACTICE 


liberate  potassium  or  ammonium;  and  potassium  to  liberate 
ammonium;  the  converse  of  the  above.  This  is  termed 
mass  action.  When  heavy  applications  of  lime  are  made, 
mass  action  ensues  and  much  stored- up  plant  food  is 
liberated. 
•     Certain  salts  have  the  power  of  absorbing  water  from 


Fig.  46. — Opening  up  a  trench  after  blasting;    extraction  of   caliche 
by  piece  work. 


the  atmosphere.  This  property  is  termed  deliquescence. 
A  very  deliquescent  material  may  be  hard  to  preserve 
in  a  good  mechanical  condition,  as  it  may  absorb  enough 
moisture  to  become  sticky  or  even  to  dissolve  in  the  water 
taken  in. 

93.  Potassium  Nitrate,  "  Niter,"  "  Saltpeter."  This 
salt  is  the  least  deliquescent  of  the  three  common  commer- 
cial  nitrates.     It   contains   nitrogen   and   potassium   both 


NITROGEN 


127 


in  comparatively  large  percentages.  The  pure  salt,  KNO3, 
contains  nearly  14  per  cent  of  nitrogen,  and  over  41  per 
cent  of  potassium  oxide.  In  commerce,  the  percentages 
run  1  or  2  per  cent  lower  than  these  figures.  Potassium 
nitrate  is  extensively  mined  in  India;  but  there  is  a  large 
demand  for  it  in  the  arts,  especially  for  the  manufacture 


Fig.  47. — Loading  caliche  on  railway  trucks. 

of  gunpowder,  consequently  the  cost  is  so  high  that  little 
finds  its  way  into  the  fertilizer  trade.  Potash  salts  from 
the  Stassfurt  deposits  in  Germany  have  been  the  chief 
sources  of  potassium,  but  other  compounds  containing 
nitrogen  are  much  cheaper  sources  of  that  element  than  is 
potassium  nitrate. 

94.  Sodium   Nitrate,    "  ChiU   Saltpeter,"    "  Soda   Salt- 
peter."    Deposits  of  sodium  nitrate   (NaNOs)   are  found 


128 


CHEMISTRY  OF  FARM  PRACTICE 


generally  in  the  soils  of  arid  or  semi-arid  regions,  but  only 
in  a  few  regions  is  there  a  percentage  high  enough  to  war- 
rant their  leaching  and  purification.  Very  extensive  de- 
posits are  located  on  the  western  coast  of  South  America, 
principally  in  Chili,  whose  government  derives  a  large 
income  from  this  som'ce.     The  deposit  is   called   caliche, 


Fig.  48. — General  view  of  crystallizing  pans  for  obtaining  nitrate  of 
soda.  Each  pan  has  about  500  cu.  ft.  capacity  and  225  sq.  ft. 
cooling  surface. 

and  occurs  at  depths  ranging  from  10  inches  to  16  feet  from 
the  surface  of  the  soil.  The  layers  containing  the  sodium 
nitrate  vary  in  thickness  from  6  inches  to  3  feet.  This 
material  is  generally  covered  with  a  kind  of  conglomerate 
rock  called  costra.  These  beds  are  from  15  to  90  miles 
distant  from  the  sea-coast  and  extend  220  miles  in  length 
and  in  some  places  2  miles  in  breadth.     It  is  believed  that 


NITROGEN 


129 


they  were  formed  comparatively  recently  and  are  due 
to  the  nitrification  of  marine  vegetation;  that  continued 
leachmgs  from  soils  accumulated  in  great  lakes  in  which 
much  vegetable  material  grew  and  accumulated;  and  that 
finally  these  lakes  became  isolated,  and  evaporation  and 
rapid  nitrification  took  place.     The  presence  of  iodine  in 


Fia.  49. — Deposit  of  nitrate  crystals  in  the  pans  of  Fig.  48  after  the 
liquor  is  run  off.  ^ 

the  caliche  would  seem  to  support  the  theory  of  marine 
formation.  There  are  a  number  of  impurities  in  the  natural 
sodium  nitrate,  among  which  are  organic  matter,  common 
salt,  calcium  sulphate,  and  insoluble  silica. 

Some  niter  deposits  have  been  found  in  California, 
though  these  are  not  of  so  high  grade  as  those  of  Chili. 
An  average  of  more  than  a  hundred  analyses  of  these  Cali- 


130 


CHEMISTRY  OF  FARM  PRACTICE 


fornia  claims  shows  a  sodium  nitrate  content  of  about 
9|  per  cent.  The  low  niter  content  and  poor  transpor- 
tation facilities  have  prevented  the  development  of  these 
deposits.  About  1,750,000  tons  of  nitrate  of  soda,  con- 
taining about  15^  per  cent  nitrogen,  are  annually  shipped 
out  of  Chili,   about  one-tenth  of  which  comes  direct  to 


Fig.  50. — Drying  floors  and  bagging  of  nitrate  of  soda. 


the  United  States.     Some  of  the  European  supply  is  also 
reshipped  to  this  country. 

95.  Calcium  Nitrate.  After  many  unsuccessful  attempt^ 
the  compound,  calcium  nitrate,  is  now  manufactured  com- 
mercially in  this  country  and  abroad  from  nitrogen  of 
the  atmosphere  by  electrolytic  means.  In  Notodden,  Nor- 
way,  where  the  large  water-power  is  utilized  to  produce 


NITROGEN  131 

electric  energy,  three  factories  have  been  established,  where, 
in  1911,  there  was  manufactured  calcium  nitrate  to  the 
value  of  $350,000.  Air  at  the  rate  of  25,000  liters  per 
minute  is  sent  through  the  electric  arcs  spread  by  powerful 
electro  magnet.  About  1  per  cent  of  the  total  volume  of 
gas  is  oxidized  to  nitric  oxide  (NO).  This  oxide  leaves  the 
apparatus  through  a  tube  kept  at  a  temperature  of  500-700° 
Centigrade;  the  gases  are  then  rapidly  cooled  to  50-60 "^ 
C,  a  temperature  favorable  to  the  further  oxidation  of 
the  nitric  oxide  to  nitrogen  tetroxide  (NO2).  This  product 
reacts  with  water  to  produce  nitric  and  nitrous  acids. 
The  equation  expressing  this  reaction  is 

•  2NO2 +H2O  =  HNO3 + HNO2. 

The  nitric  products  that  fail  to  be  absorbed  in  the  water 
are  caught  in  a  milk  of  lime  trap  as  calcium  nitrate  and 
calcium  nitrite.  The  latter  is  liberated  as  nitrous  oxide 
by  treating  with  nitric  acid.     The  reaction  is 

Ca(N02)2+2HN03  =  2HN02+Ca(N03)2. 

The  nitrous  oxide  is  again  put  through  the  process  of  con- 
version into  nitric  acid.  At  least  95  per  cent  of  the  oxide 
of  nitrogen  formed  is  transformed  into  nitric  acid  of  50 
per  cent  strength.  The  nitric  acid  is  converted  into  nitrate 
of  lime  by  adding  it  to  the  correct  quantity  of  calcium 
carbonate,  according  to  the  reaction 

2HN03+CaC03  =  Ca(N03)2+C02+H20. 

The  nitrate  of  lime  formed  is  75  to  80  per  cent  pure,  and 
contains  about  13  per  cent  of  nitrogen.  This  material 
must  be  shipped  in  casks  on  account  of  its  deliquescence. 
The  deliquescence  of  normal  calcium  nitrate  has  led  to 
the  manufacture  of  some  basic  nitrate  of  lime,  which  is 
accomplished  by  the  addition  of  the  proper  amount  of 
quicklime  to  the  hot  solution.     The  equation  is 

CaO+Ca(N03)2  =  Ca20(N03)2. 


132  CHEMISTRY  OF  FARM  PRACTICE 

Basic    calcium    nitrate    contains    about    10    per    cent    of 
nitrogen.  \ 

96.  Ammonitun  Sulphate.  This  material  is  a  by-prod- 
uct of  the  gas-works,  bone  distilleries,  and  coke-ovens.  It 
contains  about  24  per  cent  of  ammonia,  and  is  soluble  in 
water.  Its  action  in  the  soil  has  already  been  discussed. 
It  is  a  good  source  of  nitrogen  for  plant  food,  but  it  is 
higher  in  price  than  is  nitrate  of  soda. 

97.  Organic  Sources  of  Nitrogen.  The  organic  com- 
pounds containing  nitrogen  vary  greatly  in  their  agri- 
cultural value. 

Animal  Sources:  (a)  Dried  blood  is  a  by-product  of 
the  slaughter-houses.  It  is  carefully  saved,  because  of 
its  high  value  as  a  source  of  nitrogen.  The  fresh  blood 
contains  about  2|  per  cent  of  nitrogen,  but,  after  drying, 
the  product  contains  from  12  to  14  per  cent.  Blood  is 
an  excellent  quickly  available  source  of  nitrogen  for  use 
on  sandy  land,  and  is  highly  prized  as  a  source  of  nitro- 
gen for  sugar  cane  and  tobacco.  It  nitrifies  much  more 
rapidly  than  the  other  organic  forms  of  nitrogen. 

(6)  Dried  ground  fish  is  an  important  source  and  con- 
tains from  7  to  10  per  cent  of  nitrogen,  and  usually  from 
6  to  9  per  cent,  of  total  phosphoric  acid.  This  material  is 
obtained  as  a  mixture  of  refuse  and  whole  fish  from  the 
herring,  pilchard,  and  mackerel  fisheries.  Fish  has  long 
been  used  as  a  fertilizer.  The  first  colonists  found  the 
Indians  using  it  as  a  fertilizer  for  corn.  Fish  is  rriore 
slowly  available  than  blood,  and  consequently  more  lasting 
in  its  effects.  This  fact  enforces  the  importance  of  using 
at  least  two  sources  of  nitrogen  on  farm  crops  having  a 
long  growing  season. 

(c)  Tankage.  This  term,  variously  modified,  is  employed 
to  designate  quite  a  range  of  fertilizing  materials,  and  the 
modifying  words  should  be  carefully  noted.  There  is  a 
great  difference  between  first-class  slaughter  tankage,  con- 
sisting of  the  waste  products  of  slaughter-houses,  such  as 


NITROGEN  133 

blood,  flesh,  and  bone,  and  leather  tankage  which  may 
consist  of  leather  scraps  which  have  not  been  chemically 
treated  to  render  them  available.  Considering  the  fact 
that,  in  the  manufacture  of  leather,  the  hide  is  chemically 
treated  to  make  it  resistant  to  decomposition,  it  can  readily 
be  seen  that  untreated  leather  will  be  one  of  the  last  ma- 
terials to  nitrify.  Leather  tankage  is  useless  without 
treatment  with  sulphuric  acid,  but  where  so  treated  its 
nitrogen  is  available.  Great  care  should  be  exercised  to 
ascertain  its  value  to  the  soil  before  purchasing  any  kind 
of  leather  tankage. 

(d)  Peruvian  guano  consists  of  the  excrement  and  car- 
casses of  sea-fowls.  It  contains  high  percentages  of  both 
phosphoric  acid  and  nitrogen,  as  well  as  some  potash; 
but  its  chief  value  is  due  to  its  nitrogen  content.  Its  source 
was  noted  when  it  was  considered  as  a  source  of  phos- 
phorus. It  needs  no  treatment  before  applying.  Fresh 
guano  collected  from  some  islands  of  the  Pacific  Ocean 
contains  a  considerable  amount  of  ammonium  carbonate 
and  must  be  treated  with  sulphuric  acid  to  fix  this  ammonia 
in  the  form  of  a  sulphate,  because  the  carbonate  is  very 
volatile. 

(e)  Hoof  meal  should  be  classed  apart  from  hides,  horns, 
hair,  and  feathers.  Hoof  meal  runs  to  about  14  or  15 
per  cent  of  nitrogen,  and  it  gives  good  results  in  field  tests. 
The  chemical  methods  for  determining  availability  as  plant 
food  do  not,  as  a  rule,  show  the  real  value  of  this  material. 

(/)  Hides,  horns,  hair,  and  feathers  are  very  resistant 
to  nitrification,  and  hence  they  are  of  low  agricultural  value 
unless  treatment  with  sulphuric  acid  is  used  to  render 
the  nitrogen  available.  These  materials  all  run  high  in 
nitrogen  content,  but  their  use,  when  they  cost  much,  is 
unadvisable. 

(g)  Wool  contains  about  17  per  cent  of  nitrogen.  In 
imcleaned  wool  there  is  a  fatty  material  known  as  suint, 
which  contains  a  large  per  cent  of  potash  salts,  mainly  in 


134  CHEMISTRY  OF  FARM  PRACTICE 

the  carbonate  form,  although  some  chloride  and  sulphate 
are  present.  In  the  wool  of  British  sheep  there  is  about 
10  per  cent  of  potash  salts.  Wool  is,  also,  very  resistant 
to  nitrification. 

(h)  Bone.  Raw  and  steamed  bone  have  been  discussed 
under  sources  of  phosphorus. 

98.  Vegetable  Sources,  (a)  Cottonseed  meal  is  the  most 
important  source  of  nitrogen  of  vegetable  origin.  It  is 
very  highly  prized  as  a  feed  for  animals  on  account  of  its 
high  protein  content,  and  can  be  used  to  greater  advantage 
as  a  feed  than  as  a  fertilizer,  provided  that  the  manure 
is  carefully  conserved.  It  is  much  used  in  mixed  fer- 
tihzers,  not  only  on  account  of  the  plant  food  that  it  con- 
tains, but  on  account  of  the  fact  that  it  is  an  excellent 
material  to  keep  moisture  from  salts  which  might  absorb 
it.  Cottonseed  meal  contains  about  2  per  cent  of  avail- 
able phosphoric  acid,  6  per  cent  of  nitrogen,  and  1|  per 
cent  of  water-soluble  potash. 

(6)  Rape  meal  is  sometimes  used  as  a  fertilizer.  It 
contains  about  5  per  cent  of  nitrogen  and  l^u  per  cent 
of  phosphoric  acid.  This  meal  is  the  product  left  after 
the  removal  of  the  oil  from  rape  seed.  It  is  finely  ground 
before  being  marketed. 

(c)  Linseed  meal  is  a  by-product  of  the  manufacture  of 
oil  from  flaxseed.  The  old  process  linseed  meal  is  the 
residue  left  after  pressing  the  oil  out  of  the  crushed  flax- 
seed, either  when  cold  or  when  warm.  The  linseed  meal 
manufactured  by  the  new  process  consists  of  the  residue 
left  after  extracting  the  oil  with  naphtha.  Linseed  meal 
obtained  by  either  process  contains  about  5\  per  cent  of 
nitrogen,  lyV  per  cent  of  phosphoric  acid,  and  Ij  per  cent 
potash.     Linseed  meal  is  mainly  used  as  a  feed  for  cattle. 

(d)  Castor  pomace  is  the  residue  left  from  the  extraction 
of  castor  oil  from  the  castor  bean.  It  cannot  be  used  as 
a  stock  feed  on  account  of  poisonous  properties;  but  it 
has  value    as  a  fertihzer.     It  contains  about  5|  per  cent 


NITROGEN  135 

nitrogen,    If   per  cent  phosphoric    acid,    and    1   per  cent 
potash. 

(e)  Calcium  cyanamide  is  a  manufactured  organic  source 
of  nitrogen.  It  is  a  dark  crystalline  powder  which,  when 
exposed  to  the  air,  increases  in  weight,  due  to  the  slaking 
of  the  lime.  This  results  in  a  lessening  of  the  per  cent  of. 
nitrogen  that  it  contains,  not  by  losing  its  nitrogen,  but 
because  of  the  increased  weight  of  the  product. 

Calcium  cyanamide  is  manufactured  by  heating  a  mix- 
ture of  limestone  and  coke  in  an  electric  furnace  to  a  tem- 
perature of  1100°  C.  At  this  temperature  calcium  and 
carbon  unite  to  form  carbide  (CaC2).  The  finely  powdered 
calcium  carbide  has  purified  nitrogen  gas  passed  over  it 
when  it  is  at  a  white  heat  and  under  these  conditions  it 
will  take  up  two  atoms  of  nitrogen  according  to  the  fol- 
lowing formula: 

CaC2+N2  =  CaCN2+C. 

The  nitrogen  of  the  air  is  purified  either  by  passing  it 
over  red-hot  metallic  copper  or  by  the  fractional  distilla- 
tion of  liquid  air.  The  manufactured  product  contains  as 
impurities  carbon,  quicklime,  silica,  iron  oxide,  and  cal- 
cium sulphide,  phosphide  and  carbonate.  It  contains  about 
20  per  cent  nitrogen,  which  is  equivalent  to  57  per  cent  of 
calcium  cyanamide. 

The  impurities  in  cyanamide,  consisting  of  small  quan- 
tities of  sulphides,  carbides,  and  phosphides,  are  decom- 
posed by  the  soil  moisture  when  applied,  and,  unless  suf- 
ficient time  elapses  for  the  escape  of  these  products  of 
decomposition  that  are  harmful,  the  germination  of  seed 
is  affected.  The  American  Cyanamide  Company  claims 
that  they  have  an  improved  process  whereby  the  injurious 
impurities  are  removed.  Their  product  is  known  as  "  Im- 
proved Cyanamide,"  and  the  nitrogen  is  present  partly  as 
the  cyanamides  of  calcium  and  sodium,  and  partly  as 
nitrate   of   soda.     The   American   Fertilizer   Handbook   of 


136  CHEMISTRY  OF  FARM  PRACTICE 

1910  gives  a  proximate  analysis  of  this  material,  which 
shows  3.39  per  cent  nitrogen  in  the  form  of  nitrate,  and 
13.62  per  cent  of  nitrogen  in  the  cyanamide  form. 

Experiments  show  that  cyanamides  do  not  give  as  good 
results  as  a  fertilizer  as  does  sulphate  of  ammonia,  on 
soils  containing  an  abundant  supply  of  calcium  carbonate. 
On  acid  soils,  the  lime  content  of  the  cyannmide  should 
exert  a  good  influence. 


CHAPTER  XIV 
SOURCES  AND  USE  OF  POTASH  SALTS 

99.  Occurrence.  Potassium  is  one  of  the  ten  elements 
absolutely  essential  to  plant  growth.  Some  crops  are  es- 
pecially heavy  feeders  on  this  element,  prominent  among 
them  being  the  legumes,  the  root  crops,  the  sugar-pro- 
ducing crops,  and  tobacco.  Any  crop  is  particularly  sen- 
sitive to  a  deficiency  of  potash. 

The  main  commercial  sources  of  potash  salts  are  the 
Stassfurt  deposits.  These  deposits  are  located  in  Saxony, 
Germany,  and  extend  eastward  from  the  Harz  Mountains 
to  the  Elbe  River  about  60  miles,  and  from  the  city  of 
Magdeburg  southward  to  the  town  of  Bernburg  about 
20  miles.  The  deposits  of  these  salts  in  this  region  are  amply 
sufficient  to  supply  the  world  for  many  centuries. 

These  deposits  are  the  result  of  the  evaporation  of 
an  ancient  inland  sea  which  became  isolated  from  the 
ocean.  During  the  time  of  this  evaporation,  the  climate 
of  the  section  in  question  is  supposed  to  have  been  trop- 
ical. As  the  evaporation  continued,  various  salts  crys- 
tallized out  in  the  order  of  their  insolubility.  The  lowest 
stratum  consists  of  sulphate  of  lime,  CaS04;  the  next 
stratum  consists  of  rock  salt,  which  in  places  reaches  a 
thickness  of  3000  feet;  the  third  stratum  is  the  mineral, 
which  consists  of  sulphate  of  lime,  potash,  and  magnesia. 
Above  this  stratum  comes  the  kieserit  region,  where  there 
is  a  layer  of  sulphate  of  magnesia,  and  upon  it  rests  a 
deposit  of  carnallite,  which  is  a  mixture  of  potassium  chloride 
and  magnesium  chloride.  The  carnallite  deposit  varies  in 
thickness  from  50  to  130  feet.  This  deposit  yields  most 
of  the  crude  potash  from  which  the  more  concentrated 

137 


138 


CHEMISTRY  OF  FARM  PRACTICE 


salts  are  produced.     Kainit  and  sylvinit  are  found  in  adja- 
cent  deposits.     The   kainit   consists   mainly   of   potassium 


IB      ^ 

stn 

.fa     o3 

=^  H< 

—  S-l 

o 

8  3 

03    I — . 

-  a> 

1^ 
=^    >. 

>  » 


t^ 


sulphate,    magnesium   sulphate,    magnesium    chloride,    and 
sodium  chloride,  along  with  small  quantities  of  potassium 


SOURCES  AND  USE  OF  POTASH  SALTS  139 


Fig.  52. — Individual  cotton  stalk  grown  without  special  fertilizer. 


140  CHEMISTRY  OF  FARM  PRACTICE 

chloride  and  calcium  sulphate.  Sylvinit  consists  mainly  of 
potassium  chloride  and  sodium  chloride.  Overlying  the 
potash  region  is  a  layer  of  impervious  clay,  which  has 
served  to  keep  out  water  and  prevent  the  loss  of  these 
salts  by  leaching.  Above  this  clay  are  the  following  strata : 
anhydrite,  gypsum,  clay,  sand,  and  limestone. 

The  value  of  these  salts  was  discovered  about  1860, 
the  potash  salts  having  formerly  been  bored  through  and 
discarded  as  worthless,  while  the  rock  salt  below  was  mined. 
Since  the  discovery  of  the  value  of  these  salts,  the  mining 
of  them  has  been  regulated  by  the  German  Government, 
which  derives  a  large  income  from  the  export  tax  which  is 
imposed. 

100.  Wood  Ashes.  Before  the  discovery  of  the  Stassfurt 
potash  deposits,  the  main  source  of  potash  was  wood 
ashes.  The  potash  content  of  these  ashes  is  in  the  car- 
bonate and  sulphate  forms.  Ashes  also  contain  a  con- 
siderable percentage  of  lime,  and  a  small  percentage  of 
phosphorus.  Ashes  from  hardwood  trees  are  higher  in 
their  potash  content  than  other  ashes.  In  conserving 
ashes  for  their  potash  content,  they  should  be  stored  in 
a  covered  pit  with  impervious  sides  and  floor,  for  the  potash 
is  readily  leached  out. 

101.  OrganicSources  of  Potash.  Some  organic  materials 
contain  appreciable  amounts  of  potash.  Tobacco  stalks 
and  stems  contain  from  4  to  8  per  cent  of  potash.  Cotton- 
seed and  flaxseed  each  contain  some  potash.  Cottonseed 
contains  about  11  per  cent  of  potash,  cottonseed  meal  about 
1^  per  cent,  cottonseed  hulls  about  1  per  cent,  and  cotton- 
seed hull  ashes  about  24  per  cent.  Linseed  meal  contains 
about  If  per  cent  potash. 

The  pomace  obtained  from  the  fermenting  of  wine 
contains  some  potash  and  some  nitrogen. 

102.  Minor  Sources.  Another  source  of  potash  is  kelp, 
the  ashes  of  seaweeds.  Kelp  contains  from  4  to  20  per 
cent  of  potash,  depending  upon  the  seaweed  burned. 


SOURCES  AND  USE  OF  POTASH  SALTS  141 


Fig.  53. — Cotton  stalk  grown  in  same  soil  as  that  of  Fig.  52,  fexLilized 
with  phosphoric  acid  and  nitrogen. 


142 


CHEMISTRY  OF  FARM  PRACTICE 


Fig.  54. — Cotton  stalk  grown  in  same  soil  as  that  of  Fig.  52,  fertilized 
with  phosphoric  acid,  nitrogen  and  potash. 


SOURCES  AND  USE  OF  POTASH  SALTS 


143 


An  inorganic  source  of  potash  that  seems  to  offer  some 
possibilities  is  the  mineral  alunite,  which  exists  in  large 
deposits  in  some  of  our  western  States.  This  material 
contains  aluminium  sulphate  and  potassium  sulphate,  and, 
when  burned,  the  aluminium  sulphate  is  decomposed, 
leaving  alumina,   which  is  insoluble  in  hot  water,   while 


Fig.  55. — Sweet  potatoes  grown  without  fertilizer. 


potassium  sulphate  is  quite  soluble  and  can  be  removed 
by  lixiviation. 

At  the  prices  that  have  formerly  prevailed,  the  Stass- 
furt  salts  have  crowded  the  other  sources  out  of  the  gen- 
eral market. 

103.  Commercial  Salts  of  Potash.  Two  of  these  salts, 
kainit  and  sylvinit,  already  mentioned  in  Sec.  99,  are 
exported  and  sold  in  the  crude  state.  Kainit  is  a  crys- 
talline gray  material  with  some  red  and  yellow  particles. 


144 


CHEMISTRY  OF  FARM  PRACTICE 


It  contains,  as  a  rule,  between  12  and  13  per  cent  of 
potash  (K2O).  Sylvinit  is  similar  in  appearance  to  kainit; 
but  it  is  redder  in  color.  It  is  someties  sold  as  kainit, 
and  contains  a  slightly  higher  percentage  of  potash,  rang- 
ing from  12^  to  15  per  cent  of  potassium  oxide  (K2O). 
The  disadvantage  in  the  use  of  these  salts  is  that  they 


m 

% 

Hff— ;^^« 

t^M^^ 

mi^^^k    ^! 

fcaBy^Si^  <!fejKy*Ni^^^^>^N#^..^.          "J 

^,^-fX^ 

'tlib 

Fig.  56. — Sweet  potatoes  grown  on  same  soil  as  those  of  Fig.  55  but 
fertilized  with  phosphoric  acid  and  nitrogen. 


are  more  expensive  per  pound  of  potash  delivered  on  the 
farm  than  the  purified  salts.  This  is  due  to  the  fact  that 
the  transportation,  charges  on  a  pound  of  potash  in  the 
form  of  kainit  are  four  times  those  on  the  same  amount 
of  potash  in  the  form  of  muriate  of  potash,  because  kainit 
contains  12  to  13  per  cent  potash,  while  muriate  contains 
from  48  to  52  per  cent. 

The  purified  potash  salts  on  our  market  are  muriate 


SOURCES  AND  USE  OF  POTASH  SALTS 


145 


of  potash,  sulphate  of  potash,  double  sulphate  of  potas- 
sium and  magnesium,  double  manure  salts,  and  potas- 
sium-magnesium carbonate. 

104.  The  Functions  of  Potash.  Potash  in  the  soil 
favors  the  formation  of  the  carbohydrates,  such  as  starches, 
sugars,  and  cellulose  in  the  plant.     It  is  very  beneficial 


Fig.  57. — Sweet  potatoes  grown  on  the  same  soil  as  those  of  Fig.  55 
but  fertiUzed  with  potash,  phosphoric  acid  and  nitrogen. 


to  such  root  crops  as  mangolds,  sugar-beets,  Irish  potatoes, 
and  sweet  potatoes.  It  produces  marked  influences  on  the 
growth  of  leguminous  crops,  not  only  with  respect  to 
yield,  but  also  with  respect  to  the  relative  proportion 
of  the  legume  to  the  other  herbage.  Potash  induces  the 
healthy  development  of  the  leaf  and  the  stalk,  and  is 
especially  beneficial  to  grasses.  When  applied  in  large 
quantities,    potash   lengthens   the   growing   season   of   the 


146  CHEMISTRY  OF  FARM  PRACTICE 

plant.     It  also  seems  to  promote  a  more  economical  use 
of  the  soil  moisture. 

105.  The  Use  of  Potash  on  Different  Soils.  The  potash 
content  of  soils  is  very  variable,  ranging  from  yo  of  1  per 
cent  on  very  light  sandy  soils,  to  as  much  as  2  per  cent  on 
very  heavy  clay  soils. 

The  muck  soils  are  very  deficient  in  potash.  Truck  crops 
and  practically  all  crops  grown  on  light  sandy  and  muck 
soils  are  improved  by  applications  of  potash  salts.  This  is 
true  to  a  very  marked  extent  with  cotton.  On  muck  soils, 
the  yields  of  corn  are  largely  increased  by  the  use  of  potash 
salts.  In  fertilizing  general  farm  crops,  unless  there  is  some 
special  reason  that  makes  it  objectionable,  the  use  of  muriate 
of  potash  is  quite  satisfactory  and  most  economical. 

Heavy  clay  soils  contain  a  sufficient  supply  of  potash  for 
general  farm  crops,  and,  if  these  soils  are  properly  farmed  so 
that  the  conditions  for  bringing  stored  up  plant  food  into 
availability  are  accentuated,  there  should  be  such  an 
abundant  supply  of  potash  that  it  will  not  become  a  limiting 
factor  of  plant  growth.  In  fact,  field  tests  show  that  large 
amounts  of  money  are  expended  unnecessarily  each  year 
for  the  application  of  potash  to  such  soils. 

Table  XIII  shows  the  effect  of  the  use  of  potash  on  grass 
lands.  The  yield  of  hay  is  greatly  increased  and  the  growth 
of  leguminous  plants  stimulated  while  the  percentage  of 
weeds  is  markedly  decreased  through  the  use  of  a  com- 
plete mineral  manure  as  compared  with  results  obtained  with 
a  fertilizer  not  containing  potash  or  with  no  fertilizer  at  all. 

106.  Selection  of  the  Source  of  Potash.  The  cheapest 
form  of  potash  for  sale  in  the  United  States  is  the  muriate 
(KCl).  This  is  manufactured  by  the  purification  of  crude 
salts,  most  of  the  impurities  being  removed.  While  muriate 
of  potash  is  a  cheap  and  effective  source  for  general  farm 
crops,  the  use  of  a  potash  salt  containing  chlorine  injures 
the  burning  qualities  of  tobacco,  lowers  the  starch  content 
of  Irish  and  sweet  potatoes,  and  hinders  the  crystallization 


SOURCES  AND  USE  OF  POTASH  SALTS 


147 


09 

-4-3 

3 
O 


6 


148 


CHEMISTRY  OF  FARM  PRACTICE 


TABLE  XIII.— INFLUENCE  OF  POTASH  ON  GRASS  LANDS. 

(Hall) 


Manuring. 

Dry  Hay. 

Composition  of  Herbage 
in  1902. 

Plot. 

1856 

to 
1902 

1893 

to 
1902 

Grasses. 

Legu- 
'minous 
Plants. 

Weeds. 

7 

Complete  mineral  man- 
ure  

Cwts. 

38.8 

28.1 
23.3 
21.9 

Cwts. 

36.5 

21.6 
17.8 
15.9 

Per  Cent. 
20.3 

28.8 
54.4 
34.3 

Per  Ct. 
55.3 

22.1 

15.4 

7.5 

Per  Ct. 
24  4 

8 

4 
3 

Complete  mineral  man- 
ure without  potash. .  . 
Superphosphate  only .  .  . 
Unmanured 

49.1 
30.2 
58.2 

of  the  sugar  contained  in  sugar  beets.  Sulphate  of  potash, 
double  sulphate  of  potassium  and  magnesium,  or  potassium- 
magnesium  carbonate  should  be  used  for  the  crops  named. 
Truckers  observe  that  when  potatoes  are  fertilized  with 
potassium  sulphate,  they  are  smoother  than  when  fertilized 
with  a  salt  of  potash  carrying  chlorine.  It  has  been  shown 
at  the  South  Carolina  Experiment  Station  that  the  water 
content  of  sweet  potatoes  is  higher  when  fertilized  with 
muriate  of  potash  than  when  fertilized  with  sulphate  of 
potash. 

Double  sulphate  of  potassium  and  magnesium  is  not  ex- 
tensively used  in  the  United  States.  It  contains  about 
26  per  cent  of  potash,  and  may  be  used  as  a  substitute  for 
sulphate  of  potash. 

Double  manure  salts  contain  from  20  to  30  per  cent  of 
potash.  It  is  used  to  some  extent  in  the  United  States. 
The  potash  is  mainly  in  the  form  of  a  chloride,  and  sells, 
usually,  for  more  than  does  an  equal  amount  of  potash  in 
kainit  or  in  muriate  of  potash. 

Potassium-magnesium  carbonate  is  a  dry,  white  material 
containing  from  20  to  25  per  cent  of  potash  combined  as  a 
carbonate.     It  is  highly  prized  by  growers  of  tobacco  and 


SOURCES  AND  USE  OF  POl'ASH  SALTS 


149 


S6. 


■■'^, 


<-f^ 


**^ 


fc. 


150 


CHEMISTRY  OF  FARM  PRACTICE 


a 
-a 


j3 


M 


SOURCES  AND  USE  OF  POTASH  SALTS  151 

oranges.  It  is  not  deliquescent  and,  hence,  is  easily  dis- 
tributed. 

In  connection  with  the  use  of  commercial  potash  salts 
it  is  interesting  to  note  that  plants  take  up  a  large  part 
of  their  food,  especially  in  the  form  of  potassium  and  phos- 
phorus, and  store  it  in  the  early  stages  of  development;  while 
nitrogen  is  taken  up,  and  carbonaceous  material,  such  as 
starches  and  sugars,  is  for  the  most  part  formed  in  the  later 
stages  of  the  plants'  development.  This  emphasizes  the 
importance  of  applying  the  potash  salts  and  the  phos- 
phorus-bearing fertilizers  before  planting  the  crop,  and  the 
soluble  nitrogen  as  a  topdressing. 

107.  Tendency  to  use  too  much  Potash.  It  is  also  inter- 
esting to  remember  that  most  of  the  potash  is  stored  in  the 
leaves  and  the  stalks  of  the  plant,  and,  if  these  materials 
are  incorporated  in  the  soil  or  fed  on  the  farm  and  the  man- 
ure carefully  conserved  and  returned  to  the  soil,  there  will 
be  comparatively  a  small  loss  of  potash  from  the  soil, 
although  the  plant  makes  use  of  more  of  it  than  of  any  other 
ash  element.  This  fact,  and  the  high  content  of  potash 
present  in  most  soils,  shows  that  in  many  sections  the 
application  of  commercial  potash  is  largely  over-done.  To 
judge  his  potash  needs  accurately  the  farmer  must  thor- 
oughly understand  the  functions  of  potash,  the  composition 
and  condition  of  his  soil,  and  the  requirements  of  the  crops 
that  he  is  growing.  There  is  no  element  that  pays  so  hand- 
somely when  needed  or  is  so  valueless  when  unnecessarily 
applied. 


CHAPTER   XV 
MEASURING  PLANT  FOOD  REQUIREMENTS 

108.  Forms  of  Plant  Food.  There  are  two  forms  of 
each  element  of  plant  food  present  in  every  soil :  the  insolu- 
ble, or  unavailable;  and  the  soluble,  or  available.  The 
former  may  be  termed  the  potential  plant  food,  and  the 
latter  the  kinetic.  The  amount  of  available  plant  food  is 
the  limiting  factor  of  plant  growth,  however  much  potential 
plant  food  may  be  present.  The  unavailable  plant  food  is 
by  natural  processes  slowly  changed  chemicallj'  so  as  to 
become  soluble  and  these  changes  may  be  hastened  by 
appropriate  treatment.  The  depletion  of  the  total  food 
content  of  the  soil  must  be  avoided  by  application  of  fertilizer. 

109.  Soil  Analyses.  The  plant  food  in  the  soil  is  present 
in  salts,  minerals,  and  organic  matter,  which  vary  to  a  marked 
extent  in  their  solubility  in  different  solvents.  The  fact 
that  solvents  in  the  soil  vary  in  their  composition  and 
therefore  in  their  solvent  power  makes  it  extremely  difficult 
to  select  a  chemical  solvent  that  truly  represents  the  solvent 
power  of  the  soil  solvents;  hence  it  is  practically  impossible 
to  determine  accurately  by  chemical  means  the  absolute 
amount  of  available  plant  food  in  any  soil.  Soil  analyses 
can  only  determine  what  elements  are  present,  in  what 
form  and  in  what  amount.  They  are  suggestive  of  the 
treatment  that  should  be  given  the  soil  and,  therefore,  in 
many  ways  are  of  value;  but  it  should  be  remembered  that 
soil  analyses  do  not  afford  definite  data  of  the  amounts  of 
various  kinds  of  food  plants  may  obtain. 

Hopkins'  "  Soil  Fertility  and  Permanent  Agriculture  " 
estimates  that,  by  the  most  approved  agricultural  methods, 
2  per  cent  of  the  total  nitrogen  content,  1  per  cent  of  the 

152 


MEASURING  PLANT  FOOD  REQUIREMENTS         153 

phosphorus  content,  and  one-fourth  of  1  per  cent  of  the 
potash  content  of  the  soil  generally  can  be  made  available 
in  one  year.  If  we  have  an  analysis  of  the  soil,  we  can 
readily  calculate  the  number  of  pounds  of  each  element  of 
plant  food  that  would  become  available,  and  if  the  com- 
position of  the  crop  to  be  grown  is  known,  the  limiting 
factors  of  crop  raising  can  be  determined  with  some  degree 
of  accuracy,  provided  that  the  premises  are  correct  and  that 
unusual  seasons  do  not  exercise  undue  influence. 

110.  Methods  of  Soil  Analysis,  (a)  Collecting  and  Preparing  Sam- 
ples for  Analysis.  A  soil  sample  is  collected  by  taking  fifteen  or  twenty 
borings  at  different  and  apparently  representative  places  on  the  soil. 
The  borings  should  be  dried,  pulverized  if  necessary,  and  thoroughly 
mixed  and  roUed  on  a  large  piece  of  wrapping  paper  or  enamel  cloth; 
then  by  means  of  a  spatula  or  wooden  paddle,  quarter  the  mass  into 
four  approximately  equal  parts,  discard  two-quarters  that  are  diagonal 
to  each  other  and  continue  the  mixing,  quartering  and  discarding  until 
the  residue  amounts  to  about  a  pint.  This  residue  should  be  an  accurate 
sample  of  the  field.  A  2-inch  auger  with  a  long  stem  makes  a  good 
implement  for  collecting  soil  samples.  Taken  to  a  depth  of  6|  inches, 
an  average  soil  weighs  2,000,000  pounds  per  acre,  and  taking  the 
sample  to  this  depth  facilitates  calculations. 

After  air-drying,  the  sample  is  pulverized  to  pass  through  a  sieve 
with  round  holes  1  millimeter  or  ^  of  an  inch  in  diameter.  The  gravel 
particles  which  are  too  large  to  pass  through  are  weighed  to  determine 
the  per  cent  present  and  then  discarded.  The  sample  is  thoroughly 
mixed  and  placed  in  an  air-tight  container  for  analysis.  The  obtain- 
ing of  a  sample  which  fairly  represents  the  soil  is  of  the  utmost  im- 
portance, and  time  and  care  in  this  process  are  necessary. 

(b)  Acidity  or  Alkalinity.  Ten  grams  of  soil  are  shaken  with  100 
cubic  centimeters  of  distilled  water  in  a  suitable  flask  and  allowed  to 
stand  over  night.  The  liquid  is  then  decanted  through  a  fUter  paper 
and  50  cubic  centimeters  are  placed  in  a  beaker,  2  or  3  drops  of  phenol- 
phthalein  added,  the  beaker  covered  with  a  watch-glass  and  boiled  to 
a  volume  of  5  cubic  centimeters  unless  a  pink  color  appears  before  that 
degree  of  concentration.  If  no  color  appears  the  soil  is  neutral  or  acid, 
while  if  a  pink  color  appears  it  is  evidence  that  the  soil  is  alkaline. 

A  very  simple  test  for  the  reaction  of  a  soil  may  be  made  by  plac- 
ing a  strip  of  blue  litmus  paper  and  a  strip  of  red  litmus  paper  in  the 
bottom  of  a  timibler,  adding  the  soil  to  be  tested  to  a  depth  of  about 
1  inch  in  the  tumbler  and  then  moistening  the  soil  with  either  dis- 


154  CHEMISTRY  OF  FARM  PRACTICE 

tilled  water  or  rain  water.  At  the  end  of  an  hour  examine  the  paper 
by  looking  at  the  bottom  of  the  tumbler.  If  both  papers  are  red, 
the  soil  is  acid;  if  both  are  blue,  it  is  alkaUne,  and,  if  imchanged,  the 
soil  is  neutral. 

(c)  Phosphorus.  The  following  provisional  method  for  determining 
the  phosphorus  present  is  given  together  with  some  explanation  on 
page  234,  Bulletin  107  (revised)  Bureau  of  Chemistry.  Weigh  10 
grams  of  sodium  peroxide  into  an  iron  or  porcelain  crucible  and  thor- 
oughly mix  with  it  5  grams  of  the  soil.  If  the  soil  is  very  low  in  organic 
matter,  add  a  httle  starch  to  hasten  the  oxidation  action.  Heat  the 
mixture  carefully  by  applying  the  flame  of  a  Bunsen  burner  directly 
upon  the  surface  of  the  charge  and  the  sides  of  the  crucible  imtU  the 
action  starts.  Quickly  cover  the  crucible  until  the  reaction  is  over 
and  keep  at  a  low  red  heat  for  fifteen  minutes.  Do  not  allow  fusion 
to  take  place.  By  means  of  a  large  funnel  and  a  stream  of  hot  water, 
transfer  the  charge  now  free  from  organic  matter  to  a  500  cubic  centi- 
meter graduated  flask.  Acidify  with  hydrochloric  acid  and  boU.  Let 
cool  and  make  up  to  the  mark  with  distilled  water.  If  the  action  has 
taken  place  properly,  ther»  should  be  no  particles  of  undecomposed 
or  colored  soil  in  the  bottom  of  the  flask.  Allow  the  sihca  to  settle 
and  draw  off  200  cubic  centimeters  of  the  clear  solution. 

Precipitate  the  iron,  alumina,  and  phosphorus  with  ammonium 
hydroxide  added  in  slight  excess  to  the  warm  solution,  heat,  stir, 
filter  and  wash  several  times  with  hot  water,  discarding  the  filtrate. 
Return  the  precipitate  to  the  beaker  with  a  stream  of  hot  water,  hold- 
ing the  inverted  funnel  over  the  beaker,  retaining  the  filter  paper  in 
the  funnel,  and  dissolve  the  precipitate  in  hot  hydrochloric  acid,  pour- 
ing acid  upon  the  filter  to  dissolve  any  precipitate  remaining  and  add 
this  acid  washing  to  the  dissolved  precipitate.  Evaporate  the  solu- 
tion and  washings  to  complete  dryness  on  a  water  bath  to  dehydrate 
the  silica.  Take  up  with  dilute  hydrochloric  acid,  heating  if  necessary, 
and  filter  out  the  silica.  Evaporate  the  filtrate  and  washings  to  about 
10  cubic  centimeters,  add  2  cubic  centimeters  of  concentrated  nitric 
acid,  and  just  neutralize  with  ammonium  hydroxide.  Clear  up  with 
nitric  acid,  avoiding  an  excess.  Heat  at  40  to  50°  on  a  water  bath, 
add  15  cubic  centimeters  of  molybdic  solution,  keeping  at  this  temper- 
ature for  from  one  to  two  hours.  The  molybdic  solution  is  made  aT 
follows:  Dissolve  100  grams  of  molybdic  acid  in  417  cubic  centimeters 
of  ammonia  sp.  gr.  .96  and  pour  the  solution  slowly  into  1250  cubic 
centimeters  of  nitric  acid  sp.  gr.  1.20,  keep  the  mixture  in  warm  place 
for  several  days  or  vmtil  a  portion  heated  to  40°  C.  deposits  no  yellow 
precipitate.  Decant  the  solution  for  any  sediment.  Let  stand 
over  night,  filter,  and  wash  free  of  acid  with  a  -^  per  cent  solution  of 


MEASURING  PLANT  FOOD  REQUIREMENTS         155 

ammonium  nitrate  and,  finally,  once  or  twice  with  cold  water.  Trans- 
fer the  filter  to  a  beaker,  and  dissolve  in  standard  potassium  hydroxide 
(1  cubic  centimeter-0.2  milligram  P),  titrate  the  excess  of  potassium 
hydroxide  with  standard  nitric  acid  of  the  same  concentration  as  the 
KOH  solution,  using  0.5  cubic  centimeter  of  phenolphthalein  as  in- 
dicator. Subtract  the  number  of  cubic  centimeters  of  acid  used  from 
the  cubic  centimeters  of  KOH  used,  and  multiply  the  remainder  by 
.0002  and  the  result  will  be  the  grams  of  phosphorus  present  in  200  cubic 
centimeters  of  the  soil  solution.  Determine  the  amount  present  in 
500  cubic  centimeters,  and  dividing  by  the  weight  of  soil  taken  for 
analysis  (5),  multiplying  by  100  will  give  the  per  cent  of  phosphorus 
present. 

(d)  Nitrogen.  Seven  grams  of  soil  are  weighed  into  a  large  Kjel- 
dahl  flask,  0.7  gram  of  mercuric  oxide  is  added,  and  to  this  is  added 
about  20  cubic  centimeters  of  cone,  sulphuric  acid.  The  contents 
of  the  flask  are  boiled  and  digested  until  colorless.  Finely  powdered 
potassium  permanganate  is  added  while  the  contents  of  the  flask  are 
hot,  until  a  green  solution  furnishes  assurance  that  the  oxidation  is 
complete.  After  cooling,  about  250  cubic  centimeters  of  water  are 
cautiously  added,  then  enough  potassium  sulfide  solution  to  pre- 
cipitate out  the  mercury,  and  some  zinc  fiUngs  to  lessen  the  bumping 
on  boihng.  Enough  strong  alkali  is  then  added  to  neutrahze  the  acid 
and  leave  the  solution  strongly  alkaline.  The  flask  is  immediately 
connected  to  a  still  and  the  ammonia  distilled  off  into  a  standard 
solution  of  sulphuric  acid.  The  excess  of  acid  is  titrated  with  standard 
sodium  hydroxide  solution  of  the  same  concentration  as  the  sulphuric 
acid,  using  an  alcoholic  extract  of  cochineal  as  an  indicator.  Deter- 
mine the  number  of  cubic  centimeters  of  acid  neutrahzed  by  the 
ammonia  and  multiply  this  by  the  nitrogen  factor  of  the  acid.  In  case 
the  acid  is  Fifth  Normal  this  factor  will  be  .0028.  Divide  the  grams  of 
nitrogen  by  the  weight  of  the  sample  and  multiply  by  100  and  the 
result  will  be  percentage  of  nitrogen. 

(e)  Total  Potassium.  This  test  is  carried  out  as  given  on  page  147, 
Bulletin  105,  Bureau  of  Chemistry,  Department  of  Agriculture.  One 
gram  of  soil,  very  finely  pulverized,  1  gram  of  ammonium  chloride, 
and  8  grams  of  calcium  carbonate  thoroughly  ground  in  an  agate 
mortar  are  fused  as  directed  in  Fresenius'  "  Quantitative  Analysis," 
Vol.  2,  page  1175,  and  by  Hillebrand  in  Bulletin  305  of  the  United 
States  Geological  Survey,  where  an  illustration  of  the  apparatus  is 
given.  The  fused  mass  is  transferred  to  a  porcelain  dish,  slaked  with 
hot  water,  finelj'  ground  wath  an  agate  pestle  and  transferred  to  a  filter. 
After  washing  with  about  600  cubic  centimeters  of  hot  water,  the  fil- 
trate and  washings  are  run  to  dryness  in  a  Jena  beaker,  taken  up  with 


156 


CHEMISTRY  OF  FARM  PRACTICE 


hot  water  and  again  filtered,  acidified  with  hydrochloric  acid,  con- 
centrated to  about  10  cubic  centimeters,  and  I5  cubic  centimeters  of 


s 

b 

Q 


1 

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0 

d 

X 

0 

W 

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.2 

d 

« 

aJ 

s 

73 

0 

a  platinum  chloride  solution  (10  cubic  centimeters  containing  1  gram 
platinum)  added.     This  is  then  evaporated  to  a  sirupy  consistency, 


MEASURING  PLANT  FOOD  REQUIREMENTS         157 

taken  up  and  washed  about  fifteen  times  with  80  per  cent  alcohol, 
three  times  with  ammonium  chloride  solution,  and  again  fifteen  times 
with  alcohol.  The  precipitate  is  then  washed  through  the  filter  with 
hot  water  into  a  platinum  dish,  evaporated  on  the  steam  bath  to  dry- 
ness and  heated  in  an  air  oven  at  110°  C.  for  an  hour,  cooled  in  a 
desiccator,  and  weighed  as  K2PtCl6.  Duplicate  samples  should 
not  differ  more  than  1.5  milligrams  in  the  final  weight.  The  weight 
of  K2O  can  be  determined  by  multiplying  the  weight  of  the  KsPtCU 
by  the  factor  .1941. 

A  correction  must  be  made  for  the  amount  of  potassium  in  the 
reagents,  which  is  found  by  making  a  blank  determination,  using  no 
soil. 

(Ammonium  chloride  solution  is  made  by  dissolving  200  grams 
NH4CI  in  1000  cubic  centimeters  water  and  saturating  with  K-iPtClc) 
(/)  Calcium.  Calcium  may  be  determined  as  described  by  Hop- 
kins in  his  Soil  Fertility  and  Permanent  Agriculture,  page  632.  Five 
grams  of  soil  (or  less  if  high  in  calcium)  are  decomposed  by  heating 
10  grams  of  sodium  peroxide  in  an  iron  crucible.  This  is  then  taken 
up  with  water  and  hydrochloric  acid  and  made  up  to  500  cubic  centi- 
meters, as  in  the  phosphorus  determination.  After  being  allowed  to 
settle  over  night,  200  cubic  centimeters  of  the  supernatant  solution 
are  heated  to  boiling  and  precipitated  from  the  hot  solution  with 
ammonia.  The  precipitate  is  filtered  out  on  a  15-centimeter  filter 
and  washed  with  hot  water  until  but  a  slight  test  for  chlorides  is 
given  with  silver  nitrate.  The  filtrate  is  again  evaporated  to  dryness 
and  heated  (to  dehydrate  any  remaining  silica),  taken  up  with  water 
and  hydrochloric  acid,  brought  to  a  boil,  and  ammonia  added  to  pre- 
cipitate any  remaining  aluminum.  The  precipitate  is  filtered  out  on 
a  small  filter  and  washed  with  hot  water.  It  should  not  be  washed 
more  than  necessary  to  remove  the  chlorides,  as  the  wash  water  car- 
ries aluminum  through  into  the  filtrate.  On  heating  this  filtrate  and 
allowing  it  to  stand  overnight,  more  aluminum  may  be  found  to  pre- 
cipitate out.  All  of  the  aluminum  must  be  removed  by  repeated  pre- 
cipitations. The  solution  is  then  made  slightly  alkaline  with  ammonia, 
brought  to  a  boil,  and  to  it  is  added  slowly,  while  it  is  being  stirted. 
enough  concentrated  ammonium  oxalate  solution  to  precipitate  the 
calcium  and  to  change  the  magnesium  to  the  oxalate.  After  boiling 
until  the  precipitate  has  a  granular  appearance,  it  is  allowed  to  stand 
three  hours  or  longer,  decanted  into  a  filter,  and  washed  twice  by  decan- 
tation.  The  precipitate  in  the  beaker  is  then  dissolved  with  a  few 
drops  of  hydrochloric  acid,  a  little  water  added,  and  the  calcium 
reprecipitated,  boiling  hot,  by  adding  ammonium  hydroxide  to  slight 
alkalinity.     A  little  ammonium  oxalate  is  added,  the  solution  allowed 


158  CHEMISTRY  OF  FARM  PRACTICE 

to  stand  as  before,  and  filtered  through  the  same  filter,  washed  free 
from  chlorides  with  hot  water,  the  filter  burned  and  the  precipitate 
ignited  in  a  blast  until  it  ceases  to  lose  weight,  and  weighed  as  calcium 
oxide  (CaO).  This  weight  multiplied  by  the  factor  of  calcium  in 
calcium  oxide  (7129)  wiU  give  the  weight  of  calcium  from  which  the 
percentage  may  be  obtained  by  dividing  by  weight  of  the  sample 
taken  for  analysis. 

111.  Field  Tests.  The  best  measure  of  the  amount  of 
available  plant  food  in  a  soil,  and  of  food  deficiencies,  is 
obtained  by  actual  field  tests  extending  over  a  number  of 
years  to  eliminate  varying  seasonal  conditions  and  using 
as  many  crops  as  possible  to  test  out  crop  peculiarities.  On 
account  of  the  expensive  nature  of  such  experiments  they 
must  usually  be  left  to  the  State  Experiment  Stations,  and 
those  interested  in  soil  chemistry  will  do  well  to  study  what 
has  been  done  by  various  States  as  published  in  State 
Bulletins.  It  would  be  of  great  value  if  test  farms  could  be 
maintained  on  every  large  and  distinct  soil  type.  The  crops 
that  are  generally  grown  on  this  distinct  type  should  be 
tested  in  order  that  the  information  might  be  definite,  and 
this  information  should  be  available  to  the  farmers  Uving 
within  the  area  tested  in  order  that  they  might  apply  the 
knowledge  thus  gained  in  their  own  farming. 

The  simplest  effective  form  of  field  test  consists  in  a 
number  of  plots  on  which  may  be  tested  the  value  of 
each  single  element  to  a  given  crop;  then  of  every  possible 
combination  of  two  elements;  and,  finally  of  all  elements. 
It  is  best  to  provide  as  many  duphcate  plots  as  there  are 
years  in  the  rotation  employed,  and,  in  this  way  to  pro- 
duce every  crop,  every  year,  thus  eliminating  varying  seasonal 
conditions.  These  elementary  tests  may  be  enlarged  to 
include  a  comparison  of  the  different  sources  of  each  ele- 
ment of  plant  food,  varying  relative  proportions  of  tlie  three 
most  important  elements,  nitrogen,  potassium  and  phos- 
phorus, and  different  cultural  methods  used  in  connection 
with  fertihzing.  A  combination  of  two  sources  of  nitrogen 
is  often  most  effective. 


MEASURING  PLANT  FOOD  REQUIREMENTS 


159 


bO 

a 
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> 


160 


CHEMISTRY  OF  FARM  PRACTICE 


Table  XIV  shows  an  effective  three-year  test,  using  the 
common  three-year  rotation  so  much  advised  for  Southern 
conditions. 


TABLE  NO.  XIV.— AN  ELEMENTARY  FERTILIZER  TEST  IN 
CONNECTION   WITH  A  THREE- YEAR  ROTATION 

Corn  and  Cowpeas,  Followed  by  Oats  ok  Oats  and  Vetch, 
Followed  by  Cowpeas,  Followed  by  a  Cover  Crop,  Pref- 
erably a  Legume  Followed  by  Cotton,  Followed  by  a 
Cover. 


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Oats  or  Oats  and  Vetch  Followed  by  Cowpeas,  Followed  by  a 
Cover  Crop,  Preferably  a  Legume,  Followed  by  Cotton, 
Followed  by  a  Cover  Crop,  Followed  by  Corn  and  Cow- 
peas. 


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MEASURING  PLANT  FOOD  REQUIREMENTS         161 


TABLE  NO.  XIY.— Continued. 

Cotton  Followed  by  a  Cover  Crop,  Followed  by  Corn  and 
CowPEAS,  Followed  by  Oats  or  Oats  and  Vetch,  Followed 
BY  Cowpeas,  Followed  by  a  Cover  Crop. 


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Z 

The  plan  as  outlined  serves  to  show  a  simple  fertilizer 
test  in  connection  with  a  three-year  rotation;  it  may  be 
enlarged  or  modified  to  cover  any  desired  scope  or  condi- 
tion, or  it  may  be  used  simply  to  test  a  single  crop.  In 
making  fertilizer  tests,  the  most  approved  agricultural 
methods  for  maintaining  fertility  should  be  followed,  unless 
the  object  of  the  experiment  is  to  determine  the  plant  food 
requirements  under  a  one-crop  system. 

The  individual  farmer  should  avail  himself  of  all  the  data 
issued  by  his  own  and  neighboring  Experiment  Stations, 
and  it  will  often  prove  profitable  for  him  to  conduct  simple 
tests  himself.  He  should  be  familiar  with  the  plant  food 
content  of  his  various  soil  types,  procured  by  soil  analyses, 
for  this  shows  the  amount  of  potential  plant  food  in  his 
soil,  and  he  has  at  his  command  the  various  agencies  already 
discussed  for  bringing  this  food  into  availability. 


CHAPTER  XVI 
MIXING  OF  FERTILIZERS 

112.  Advantages  of  Home-Mixing.  Phosphorus,  ni- 
trogen and  potassium  are  the  three  elements  most  usually 
found  necessary  to  be  supplied  to  a  soil  to  keep  up  its 
fertility.  The  sources  of  these  elements  have  been  dis- 
cussed. The  next  consideration  is  how  to  apply  most  eco- 
nomically these  purchased  plant  foods. 

Fertilizer  factories  are  equipped  with  machinery  that  will 
mix  thoroughly  the  raw  materials,  provided  their  work  is  well 
done.  That  this  work  is  not  always  thoroughly  done  and 
that  the  materials  are  not  always  compounded  so  as  to  ap- 
proximate the  desired  mixture,  is  readily  seen  by  examining 
any  of  the  many  Fertilizer  Control  Reports  issued  from  the 
various  Experimental  Stations.  When  fertihzing  materials 
are  mixed,  it  is  extremely  difficult  to  determine  with  any 
degree  of  exactness  the  kind  and  proportion  of  all  of  the 
raw  materials  used.  Due  to  this  fact,  a  small  amount  of 
cheap  and  unavailable  plant  food,  especially  low-priced 
nitrogen,  can  be,  and  often  is,  worked  into  the  mixture.  The 
fertUizer  manufacturers  charge  for  mixing  from  $3  to  $7  per 
ton.  There  are  a  number  of  formulas  that  farmers  have 
become  accustomed  to  buy  of  which  some  are  very  low  grade. 
In  mixing  such  formulas,  the  manufacturer  must  necessarily 
add  some  "  make- weight  "  to  his  high-grade  materials  to 
bring  the  mixture  to  the  desired  percentage.  This  "  make- 
weight "  is  known  as  the  filler. 

The  transportation  and  hauling  of  filler  is  a  heavy  and 
unnecessary  expense  that  can  be  avoided  by  the  purchase 
and  home-mixing  of  high-grade  materials.  The  greatest 
advantage  to  be  gained  by  the  home-mixing  of  commercial 

1G2 


MIXING  OF  FERTILIZERS 


163 


fertilizers  lies  in  the  fact  that  the  sources  from  which  the 
phosphorus,  nitrogen,  and  potash  are  derived  are  then  known. 
A  thorough  knowledge  of  the  relative  availabilities  of  the 
different  sources  of  commercial  fertiUzers,  and  of  their 
actions  under  different  crops,  will  enable  the  farmer  to  select 
wisely  materials  the  fertilizing  values  of  which  are  known. 

113.  Fertilizers  may  be  Thoroughly  Mixed  on  the  Farm. 
The  mixing  of  fertilizers  can  be  thoroughly  done  on  any 
farm,  as  has  been  shown  by  the  South  Carolina  Experi- 
ment Station.     When  practicable,  an  out-building  with  a 


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1 


Fig.  63. — Diagram  showing  relative  composition  and  value  of  fertilizers: 
A,  low  grade;  B,  medium  grade;  C,  high  grade.  (Farmers' 
Bulletin  457,  U.  S.  Dept.  Agr.) 

tight  floor  is  preferable  for  the  mixing,  because  the  work 
can  be  done  when  weather  conditions  would  prevent  out- 
side work.  If  no  tight  floor  is  available,  one  may  be  made, 
preferably  under  a  shed,  by  taking  straight-edged  boards 
about  1  inch  in  thickness,  laying  them  on  a  level  place 
and  keying  them  up  tight.  A  floor  8  feet  wide  and  12  feet 
long,  surrounded  on  three  sides  by  upright  boards  12  inches 
wide,  will  suffice  for  the  mixing. 

The  raw  materials  are  generally  purchased  in  sacks.  If 
a  sufficient  quantity  is  mixed  to  warrant  the  pm-chase  in 
car-load  bulk  shipments,  it  will  usually  be  advisable  to  buy 


164 


CHEMISTRY  OF  FARM  PRACTICE 


a  machine  for  mixing.  The  formula  having  been  worked 
out,  and  knowing  that  1000  pounds  makes  a  good  quantity  for 
two  men  to  manipulate,  one-half  of  the  materials  necessary 
to  make  a  ton  of  fertilizer  is  poured  in  the  middle  of  the 
floor  in  alternate  layers,  beginning  preferably  with  the  acid 
phosphate.  Two  men  can  perform  the  mixing  most  ad- 
vantageously, one  mixing  with  a  hoe,  and  the  other  with  a 
spade  or  shovel.  In  the  case  of  the  mixture  made  at  the 
Station  referred  to,  the  mass  was  hoed  and  shoveled  first 
to  one  corner,  then  to  the  other  corner,  and  once  diagonally 
across  the  8  by  12  floor.  Samples  were  taken  of  the  un- 
mixed materials  and  of  the  mixed  materials.  Table  XV 
may  be  taken  as  a  typical  analysis  of  the  result  of  such 
mixing. 


TABLE     XV.— AN     EXAMPLE     OF     THE     THOROUGHNESS 
OF  HOME-MIXING   OF  FERTILIZERS 


Lbs.  of  To- 
tal Phos- 
phoric Acid 
(P2O6). 

Lbs.  of  Ni- 
trogen (N) 
Equivalent 
to  Ammonia 

(NHs). 

Lbs.  of  Wa- 
ter-soluble 
Potash 
(K2O) 

800  lbs.  17.28%  (P2O5)  acid  phos- 

'  phate  contains 

400    lbs.    8.14%     (NH3)     2.91% 
(P2O5)  1.70%  (K2O)  cottonseed 
meal  contains 

138.2 
11.6 

32.6 

6.8 

65  lbs.  48.06%    (Kj)  muriate  of 
potash  contains 

31.2 

1265  lbs 

149.8 
11.84 
11.77 

32.6 
2.58 
2.76 

38.0 

Mixture  contained  theoretically.  . 
Mixture  analyzed 

3.00 
3.01 

In  making  a  home-mixture,  it  is  very  desirable  to  use 
some  material  that  acts  as  a  good  dryer.  Cottonseed  meal 
is  a  most  excellent  dryer.  Rape  meal,  linseed  meal,  and 
muck  are  also  good  dryers. 

In  the  mixture  mentioned,  it  was  found  that  two  men 


MIXING  OF  FERTILIZERS  165 

can  mix  from  6  to  8  tons  per  day,  weighing  out  the  materials 
when  fractions  of  a  sack  are  used  and  assuming  the  weight 
on  the  sack  as  accurate  when  full  sacks  were  used.  In  the 
formula  noted,  only  the  muriate  of  potash  was  weighed. 
The  mixed  material  was  replaced  in  the  sacks  from  which 
the  raw  materials  were  removed.  The  cost  of  mixing  each 
ton  can  be  computed  by  dividing  the  wages  of  the  men  by 
the  number  of  tons  mixed.  It  will  usually  amount  to  less 
than  50  cents  per  ton. 

114.  Educational  Influence.  An  advantage  of  the  home- 
mixing  of  fertilizers,  not  often  considered,  is  that  it  necessi- 
tates a  more  thorough  knowledge  of  fertilizing  materials  and 
it  is  a  strong  incentive  to  study,  for  fertilizing  materials 
cannot  be  indiscriminately  mixed.  However,  the  incom- 
patibilities are  few  and  easily  explained.  The  chart,  Fig. 
64,  shows  the  materials  that  may  be  mixed  advantageously, 
and  the  materials  that  should  not  be  mixed.  This  chart, 
which  had  its  beginning  in  a  German  publication,  has  been 
modified  from  time  to  time  as  data  have  been  secured.  It 
is  modified  from  the  chart  given  in  Bulletin  388  of  the  Office 
of  Experiment  Stations,  because  it  has  been  shown  at  the 
South  Carolina  Experiment  Station  that  the  potash  content 
both  of  muriate  of  potash  and  kainit  is  rendered  partly 
insoluble  by  mixing  with  basic  slag  or  Thomas  phosphate; 
and  the  chart  has  been  made  to  conform  to  this  fact. 

115.  The  Calculation  of  Formulas.  Six  forms  of  cal- 
culations are  commonly  met  with  in  connection  with  the 
home-mixing  of  fertilizers. 

1.  Given  the  percentage  and  weights  of  materials; 
calculate  the  formula. 

2.  Given  the  materials  and  their  analyses  and  the  com- 
position of  the  formula  desired;  calculate  the  weight  of  each 
material  required. 

3.  Given  the  materials  too  low  in  composition  for 
making  a  formula  of  high  percentage  composition;  over- 
come the  difficulty. 


166 


CHEMISTRY  OF  FARM  PRACTICE 


4.  Given  the  high-grade  materials;  reduce  to  the  pro- 
portion of  a  low-grade  formula  and  avoid  the  use  of  a 
filler. 

5.  To  determine  the  amount  and  composition  of  a 
fertilizer  when  a  portion  is  used  under  the  crop  and  the 
remainder  as  a  side  application  or  topdressing. 

6.  To  convert  a  fertilizer  from  one  formula  to  another. 
Examples   of   each   form   of   calculation   are   given   as 

types  of  the  work  involved. 

In  the  fertilizer  trade,  the  term  unit  is  often  used.  A 
unit  is  1  per  cent  of  a  ton,  or  20  pounds.  In  making  these 
calculations,  it  must  be  remembered  that  per  cent  means 
pounds  in  a  hundred  pounds  of  material. 

(1)  The  percentage  and  weight  of  material  being  given, 
calculate  the  formula. 

Problem:  Given,  1000  pounds  of  16  per  cent  avail- 
able acid  phosphate  (P2O5),  100  pounds  of  muriate  of  potash, 
48  per  cent  water-soluble  potash  (K2O)  and  900  pounds  of 
cottonseed  meal  that  will  analyze  nitrogen  equivalent  to 
7  per  cent  ammonia  (NH3),2per  cent  phosphoric  acid  (P2O5) 
and  1.5  per  cent  of  water-soluble  potash  (K2O). 

A  good  way  to  outline  this  calculation  is  as  follows: 


1000 
900 
100 

2000 


Percentage,  Composition,  and  Source  of 
Material. 


16%  P2O5  acid  phosphate  will  fur- 
nish   

7%  NH3— 2%P206— 1.5%  K2O  C.S. 
meal  will  furnish 

48%  K2O  muriate  of  potash  will 
furnish 


Formula . 


Lbs.  of 
Nitrogen 
(N)  equiv- 
alent to 
Ammonia 
(NH3). 


63.0 


63.0 


3.15% 


Lbs.  of 
Phos- 
phoric 
Acid 
(P2O6). 


160.0 
18.0 

178.0 

8.9% 


Lbs.  of 
Water- 
Soluble 
Potash 
(K2O). 


13.5 
48.0 
61.5 
3.08% 


MIXING  OF  FERTILIZERS  167 

The  formula  is  obtained  by  dividing  the  content  in  pounds 
of  each  constituent  by  twenty,  the  number  of  hundred 
pounds  in  the  mixture,  and  the  result  is  the  number  of  pounds 
of  the  constituent  in  100  pounds  of  material,  or  the  per- 
centage composition. 

(2)  Given,  the  materials  and  their  analyses  and  the  com- 
position of  the  formula  desired;  calculate  the  weight  of  each 
material  required,  f 

Superphosphaie 

Thomas  sla^ 


Barnyard  manure 
and  guano 


- ,,-  ur  \\      I  j\        I  Norwegian  nitrate 

Lime  nitrogen     t'l^BoZJL       r\\    ^  J\       /^       ^^ .      .      .1^J3D     (l>aiiic  calcium 
(calcium  cyanamid)V«s^Qi^t\  /     V^      /   3^SC  \       ^^[     X/As^^^r       nitrate) 


Nitrate  of  soda 


Fig.  64. — Diagram  indicating  what  fertilizer  mat  rials  may  and  may 
not  be  safely  mixed.  The  dark  hnes  unite  materials  which  should 
never  be  mixed,  the  double  Hnes  those  which  should  be  apphed 
immediately  after  mixing,  and  the  single  lines  those  which  may  be 
mixed  at  any  time. 

Problem:  Make  a  fertilizer  analyzing  nitrogen  equiva- 
lent to  4  per  cent  of  ammonia,  8  per  cent  phosphoric  acid, 
and  4  per  cent  water-soluble  potash.  Use  150  pounds  of 
nitrate  of  soda  as  a  source  for  a  part  of  the  nitrogen  and 
derive  the  balance  of  the  nitrogen  from  that  contained  in 
ground  fish  scrap.  The  ground  fish  scrap  contains  nitro- 
gen equivalent  to  10  per  cent  of  ammonia,  and,  in  addition, 
6  per  cent  of  phosphoric  acid.     The  potash  is  to  be  derived 


168  CHEMISTRY  OF  FARM  PRACTICE 

from  muriate  of  potash.     The   phosphoric   acid   is  to  be 
derived  from  16  per  cent  acid  phosphate. 

This  calculation  should  be  handled  as  follows:  The 
number  of  pounds  of  plant  food  required  for  a  ton  of  this 
material  is  nitrogen  equivalent  to  80  pounds  of  ammonia, 
160  pounds  of  actual  phosphoric  anhydride  (P2O5),  and 
80  pounds  of  water-soluble  potash.  There  is  a  specified 
amount  of  one  material  to  be  used  as  a  source  of  nitrogen, 
150  pounds  of  nitrate  of  soda  which  will  contain  nitrogen 
equivalent  to  18  per  cent  of  ammonia  or  27  pounds  in  the 
150  pounds  of  material.  Nitrogen  equivalent  to  80  pounds 
of  ammonia  is  required;  so  27  pounds  furnished  by  the 
nitrate  of  soda  must  be  deducted,  leaving  53  pounds  to  be 
furnished  by  ground  fish  scrap  which  contains  nitrogen 
equivalent  to  10  per  cent  of  ammonia;  hence  it  will  require 
530  pounds  of  ground  fish  scrap  to  furnish  the  remainder 
of  the  nitrogen.  In  addition  to  the  nitrogen  content  of 
the  fish  scrap,  this  material  carries  6  per  cent  of  phosphoric 
acid,  which  is  equivalent  to  31.8  pounds  of  phosphoric  acid. 
The  amount  of  phosphoric  acid  required  is  160  pounds,  less 
32  poimds  derived  from  the  ground  fish  scrap,  leaving  128 
pounds  of  actual  phosphoric  anhydride  to  be  furnished  by 
16  per  cent  acid  phosphate.  The  number  of  hundred 
pounds  of  acid  phosphate  required  can  be  determined  by 
dividing  the  number  of  pounds  required,  128,  by  the  num- 
ber of  pounds  of  phosphoric  anhydride  contained  in  100 
pounds  of  acid  phosphate,  16,  in  this  case.  The  number 
of  hundred  pounds  of  muriate  of  potash  to  use  is  determined 
by  dividing  80,  the  number  of  pounds  of  actual  potash,  by 
48,  the  number  of  pounds  of  potash  contained  in  100  pounds; 
80-j-48  =  1.666,  or  167  pounds.  This  form  of  calculation  is 
the  one  most  used  by  fertilizer  manipulators  in  calculating 
their  formulas. 


MIXING  OF  FERTILIZERS 
Tabulating,  we  have  the  following: 


169 


■3 

•c 

►-1 

Source  and  Composition  of  Material. 

Lbs.  of 
Nitrogen 
(N)  equiv- 
valent  to 
Ammonia 

(NH,). 

Lbs.  of 
Phos- 
phoric 
Acid 
(P2O5). 

Lbs.  of 
Water- 
Soluble 
Potash 
(K,0). 

150 
530 

800 
157 
353 

18%  (NH3)  nitrate  of  soda 

10%  (NHs)  and  6%  (P2O5)  ground 

fish 

16%  (P2O5)  acid  phosphate 

48%  (K2O)  muriate  of  potash 

Make-weight  filler 

27.0 
53.0 

32.0 
128.0 

80 

2000 

Formula.        .  .    ...    

80.0 

160.0 

80 

4.0% 

8.0% 

4  0% 

(3)  Given,  material  too  low  in  composition  to  make  a 
formula  of  high  'percentage  composition;  overcome  the  difficulty. 

Problem  :  To  apply  1000  pounds  of  a  fertilizer  per  acre 
for  truck,  analyzing  nitrogen  equivalent  to  5  per  cent 
ammonia,  8  per  cent  phosphoric  anhydride,  and  8  per  cent 
potash.  Source  of  phosphoric  acid,  14  per  cent  acid  phos- 
phate; source  of  nitrogen,  ground  fish  scrap  containing  nitro- 
gen equivalent  to  10  per  cent  ammonia  and  6  per  cent  avail- 
able phosphoric  acid;  source  of  potash,  sulphate  of  potash 
containing  48  per  cent  water-soluble  potassium  oxide  (K2O). 

Apply  the  same  process  outUned  in  (2),  whereby  it  is 
found  that  1000  pounds  of  dried  ground  fish,  714  pounds 
of  14  per  cent  acid,  and  333  pounds  of  sulphate  of  potash 
contain  the  plant  food  desired  for  compounding  1  ton  of 
fertilizer  analyzing  nitrogen  equivalent  to  5  per  cent  of 
ammonia,  8  per  cent  phosphoric  anhydride,  and  8  per  cent 
water-soluble  potash;  but  that  the  mixture  weighs  2047 
pounds  instead  of  2000  pounds.  Therefore  the  plant  food 
is  mixed  in  the  same  proportions  as  a  "  5-8-8  "  fertilizer 
(fertilizer  containing  5  per  cent  ammonia,  8  per  cent  phos- 


170 


CHEMISTRY  OF  FARM  PRACTICE 


phoric  anhydride  and  8  per  cent  water-soluble  potash); 
but  due  to  the  increased  weight,  the  per  cent  is  corre- 
spondingly diminished. 

The  results  are  tabulated  as  follows: 


■c 

H 

Percentage,  Composition  and  Source  of 
Material 

Lbs.  of 
Nitrogen 
(N)  equiv- 
valent  to 
Ammonia 

(NH3). 

Lbs.  of 
Phos- 
phoric 
Acid 
(P2O6). 

Lbs.  of 
Water- 
Soluble 
Potash 
(KjO). 

714 
1000 

333 

14%  (P2O5)  acid  phosphate 

10%  (NH3)  ammonia  and  6%  phos- 
phoric anhydride  dried  ground  fish 
48%  (K2O)  sulphate  of  potash 

100.0 

100.0 
60.0 

160.0 

2047 

20.47 

100.0 

160.0 

160.0 

Formula 

4.89 

7.82 

7  82 

Therefore  the  number  of  pounds  to  be  applied  that  will 
contain  the  same  amount  of  plant  food  as  1000  pounds  of  a 
5-8-8  fertilizer  can  be  calculated  by  making  use  of  the  follow- 
ing proportion: 

2000  :  2047  =  1000  :  a;  =  1024  pounds. 

(4)  Given,  high-grade  materials;  make  to  the  'proportion 
of  a  low-grade  formula,  and  avoid  the  use  of  a  filler. 

Problem:  Calculate  a  formula  analyzing  nitrogen 
equivalent  to  3  per  cent  of  ammonia,  8  per  cent  of  available 
phosphoric  acid,  and  3  per  cent  of  water-soluble  potash, 
one-third  of  the  nitrogen  to  be  derived  from  sulphate  of 
ammonia,  which  contains  24  per  cent  of  ammonia,  and 
two-thirds  from  cottonseed  meal;  the  phosphoric  anhydride, 
from  16  per  cent  acid  phosphate;  and  the  potash,  from  48 
per  cent  muriate  of  potash.  Calculate  the  analysis  of  the 
formula  if  no  filler  is  added,  and  the  number  of  pounds  of 
this  mixture  equivalent  to  500  pounds  of  a  "  3-8-3  "  fer- 
tiUzer. 


MIXING  OF  FERTILIZERS  171 

(a)  Proceed  as  in  (3).  In  this  case  there  is  a  difference 
from  the  type  given  under  (3)  in  that  there  are  two  sources 
of  nitrogen  given,  but  the  amount  to  calculate  to  each  source 
is  also  fixed,  hence  we  find  571  pounds  cottonseed  meal, 
7-2-1.5,  will  carry  nitrogen  equivalent  to  7  per  cent  of 
ammonia  and  that  83  pounds  of  sulphate  of  ammonia 
will  carry  one  unit  of  ammonia.  The  available  phosphoric 
anhydride  not  furnished  by  the  content  of  the  571  pounds 
of  cottonseed  meal  will  be  furnished  by  932  pounds  of 
16  per  cent  acid  phosphate;  and  the  water-soluble  potash 
not  furnished  by  the  water-soluble  potash  content  of  1.5 
per  cent  contained  in  the  cottonseed  meal  will  be  furnished 
by  107  pounds  of  48  per  cent  muriate  of  potash. 

(6)  Proceed  as  in  (1).  Adding  we  find  that  1693  pounds 
of  a  mixture  of  cottonseed  meal,  sulphate  of  ammonia,  acid 
phosphate,  and  muriate  of  potash  in  the  proportions  shown 
under  (a)  contains  nitrogen  equivalent  to  60  pounds  of 
ammonia,  160  pounds  of  phosphoric  anhydride,  and  60 
pounds  of  water-soluble  potash;  hence,  if  we  divide  these 
figures  by  16.93,  we  will  obtain  the  number  of  pounds  of 
actual  plant  food  in  each  hundred  pounds  of  the  mixture 
or  the  per  cent.,  9.6  per  cent  available  phosphoric  acid, 
nitrogen  equivalent  to  3.6  per  cent  ammonia,  and  3.6  per 
cent  of  water-soluble  potash. 

(c)  The  number  of  pounds  of  this  mixture  equivalent 
to  500  pounds  of  a  3-8-3  fertihzer  is  solved  as  under  (3) : 

2000  :  1693  =  500  :  x=423  pounds. 

This  proportion  is  based  on  the  fact  that  2000  pounds, 
the  weight  of  a  ton,  is  to  1693  pounds,  the  weight  of  the 
mixture  containing  the  amount  of  plant  food  in  the  ton,  as 
500  pounds,  the  portion  of  the  ton  used,  is  to  x,  x  repre- 
senting the  proportion  of  the  mixture  equivalent  to  500 
pounds  of  3-8-3  fertilizer.  To  use  this  mixture  on  the  3-8-3 
basis  423  pounds  should  be  applied  where  500  is  called  for. 

(5)   To  determine  the  amount  and  composition  of  a  fer- 


172  CHEMISTRY  OF  FARM  PRACTICE 

tilizer  when  a  portion  is  used  under  the  crop  and  the  remainder 
as  a  side  application  or  topdressing. 

Problem:  Suppose  that  500  pounds  of  a  3-8-3  mix- 
ture is  applied  to  corn  land  before  the  crop  is  planted,  200 
pounds  of  7-5-5  mixture  is  applied  at  the  time  of  the  second 
cultivation  of  the  crop,  and  that  100  pounds  of  nitrate  of 
soda  is  appHed  when  the  plants  are  about  4  feet  tall,  what 
percentages  and  what  composition  will  the  entire  fertilization 
give? 

This  is  a  different  application  of  the  principles  given 
under  (1);  however,  the  same  type  will  serve  as  an  illus- 
tration. The  calculation  shows  that  the  entire  apphcation  is 
800  pounds  of  fertihzer  analyzing  nitrogen  equivalent  to 
5.88  per  cent  of  ammonia,  6.25  per  cent  phosphoric  acid, 
and  3.13  per  cent  of  water-soluble  potash. 

(6)  To  conver^  fertilizers  from  one  formula  to  another. 

Problem  :  Convert  a  4-8-4  fertilizer  to  a  3-9-2  formula, 
using  dried  ground  nsh,  10  per  cent  ammonia  and  6  per 
cent  available  phosphoric  acid,  and  16  per  cent  acid  phos- 
phate. Calculate  the  number  of  pounds  of  each  of  these 
materials  and  of  filler.  An  inspection  of  the  two  formulas 
shows  that  the  greatest  difference  is  in  the  potash  content 
of  the  two  formulas,  hence  the  potash  content  of  the  4-8^ 
fertilizer  will  limit  the  number  of  pounds  that  can  be  used. 
A  ton  of  4-8-4  fertilizer  contains  80  pounds  of  potash,  while 
a  ton  of  3-9-2  fertilizer  contains  only  40  pounds  of  potash, 
therefore  1000  pounds  of  the  4-8-4  fertilizer  can  be  used. 
This  leaves  20  pounds  of  nitrogen  and  100  pounds  of  phos- 
phoric acid  to  be  furnished  by  dried  ground  fish  and  acid 
phosphate.  The  nitrogen  is  the  smallest  amount  and  should 
be  supplied  first  because  the  dried  ground  fish  also  furnishes 
some  phosphorus,  which  must  be  deducted  from  the  balance 
to  be  furnished  before  the  amount  of  acid  phosphate  is  cal- 
culated. Twenty  pounds  of  nitrogen  is  furnished  by  200 
pounds  of  dried  ground  fish  analyzing  nitrogen  equivalent 
to  10  per  cent  of  amm.onia,  6  per  cent  or  12  pounds  of  phos- 


MIXING  OF  FERTILIZERS 


173 


phoric  acid  is  also  furnished,  and  this  amount,  deducted  from 
100  pounds,  leaves  88  pounds  to  be  furnished  by  16  per 
cent  acid  phosphate.  Sixteen  will  go  into  88  five  and  one- 
half  times,  hence  550  pounds  of  acid  phosphate  will  be  re- 
quired. Adding,  we  have  1750  pounds  of  material  to  which 
must  be  added  250  pounds  of  make-weight  or  filler. 

Type  of  conversion  of  fertilizer  from  one  formula  to 
another: 


"3 

Source  and  Composition  of  Material. 

Nitrogen 
equiv- 
alent to 
Lbs.  of 

Ammonia 

Lbs.  of 
Phos- 
phoric 
Anhy- 
dride. 

Lbs.  of 
Water- 
soluble 
Potash 
(KjO). 

1000 

4-8-4  fertilizer. 

40.0 
20.0 

80.0 
12.0 

88.0 

40.0 

200 

Dried  ground  fish  10%  NH3— 6% 
PaOs 

550 

16%  acid  phosphate 

250 

Filler 

2000 

60.0 

180.00 

40.0 

3.0% 

9.0% 

2.0% 

In  the  above  calculations  the  plant  food  elements  have 
been  computed  on  the  basis  of  the  phosphorus  combined 
as  phosphoric  anhydride  (P2O.5),  the  nitrogen  as  ammonia 
(NH3),  and  the  potassium  as  potassium  oxide  (K2O).  The 
reason  for  this  is  that  it  is  on  this  basis  that  it  has  become 
customary  to  buy  and  sell  the  elements. 

The  above  types  will  cover  all  of  the  contingencies  likely 
to  arise  in  the  home-mixing  of  fertilizers. 


CHAPTER  XVII 
ANIMAL    NUTRITION 

116.  Ihirposes  of  Animal  Food.  Food  serves  the  animal 
in  three  ways. 

1.  To  act  as  a  fuel  to  keep  up  the  temperature  above 
that  of  the  surrounding  air.  This  is  accomplished  by  the 
oxidation  of  the  combustible  portion  of  the  food  through- 
out the  body  in  the  capillaries  wherein  the  oxygen  in  the 
blood  corpuscles  comes  in  contact  with  combustible  matter 
in  the  blood  serum. 

2.  To  furnish  energy  by  which  the  mechanical  or  mental 
work  of  the  body  may  be  produced. 

3.  To  build  up  or  keep  in  repair  the  bodily  structures. 

117.  Classes  of  Foods.  Plants  can  sustain  themselves 
upon  very  simple  foods  such  as  water,  carbon  dioxide  and 
mineral  salts,  while  animals  are  so  constructed  that  they  de- 
mand more  highly  organized  foods  and  are  therefore  depen- 
dent upon  plant  structures  or  upon  animals  that  subsist 
upon  vegetable  food. 

Foods  of  animals  fall  into  one  of  four  classes: 

1.  Proteins.  These  are  composed  of  carbon,  hydrogen 
and  oxygen  with  a  rather  large  amount  of  nitrogen  (16  per 
cent)  and  generally  small  portions  of  sulphur  and  iron.  The 
amount  of  protein  is  calculated  by  multiplying  the  nitrogen 
content  of  the  material  by  the  factor  6.25.  Proteins  are 
utilized  by  animals  to  build  up  worn-out  muscular  tissue. 
They  are  found  in  the  gluten  of  flour,  beans,  nuts  and 
generally  in  the  seeds  of  plants,  in  lean  meat,  milk,  cheese 
and  whites  of  eggs,  as  well  as  in  various  feeds. 

2.  Carbohydrates.  These  are  made  up  of  carbon,  hydro- 
gen and  oxygen,  the  two  latter  in  the  same  proportion  as 

174 


ANIMAL  NUTRITION  175 

they  are  found  in  water.  They  supply  the  animal  with  heat 
and  energy.  Starches  and  sugars  are  carbohydrates.  Car- 
bohydrates are  also  contained  in  potatoes,  in  wheat  flour, 
oatmeal  and  other  cereals. 

3.  Fats.  These  are  composed  almost  entirely  of  carbon, 
hydrogen  and  oxygen  with  a  high  percentage  of  carbon. 
Like  the  carbohydrates  they  supply  heat  and  bodily  energy, 
having  per  pound  more  than  twice  the  value  of  the  carbo- 
hydrates. Fats  are  found  in  butter,  meat  fats  and  the  oils 
of  various  nuts.  The  fats  stored  up  in  the  body  are  mainly 
derived  from  the  carbohydrate  food. 

4.  Mineral  Compounds.  These  hjave  varied  composition, 
but  very  few  contain  carbon.  They  serve  a  variety  of  pur- 
poses in  the  body.  Water  and  the  salts  of  sodium  and  cal- 
cium are  the  most  important  articles  of  this  class  of  foods. 

118.  Development  of  a  Science  of  Animal  Nutrition. 
The  science  of  animal  nutrition  had  its  beginning  in  1859, 
when  Grouven  suggested  the  first  feeding  standard  for  farm 
animals.  Grouven's  standard  was  based  upon  the  total 
amount  of  crude  protein,  carbohydrates,  and  fat  contained 
in  the  material  fed.  Later  work  has  shown  that  this  was 
an  irrational  basis,  because  of  the  variation  in  the  digesti- 
bility of  these  proximate  constituents  in  different  animal 
feeds.  It  is  even  more  necessary  to  consider  the  digesti- 
bility of  the  feed  for  animals  than  it  is  to  consider  the  avail- 
ability of  a  fertilizing  material  for  plants,  because,  after  a 
certain  length  of  time,  the  feed  undigested  is  voided  by  the 
animal,  while  the  unavailable  plant  food  remains  in  the  soil 
and  may  later  be  made  available  by  natural  agencies. 

In  1864,  Dr.  Emil  von  Wolff  presented  a  table  of  feed- 
ing standards  based  on  the  amount  of  digestible  nutrients 
contained  in  each  particular  feeding  stuff.  Wolff's  standard 
has  siace  furnished  the  basis  for  rational  feeding  methods. 
In  1874,  ten  years  after  Wolff  published  his  standard. 
Dr.  Atwater  brought  it  to  the  attention  of  the  American 
people,   and  in   1880  Armsby  published  his   "  Manual  of 


176  CHEMISTRY  OF  FARM  PRACTICE 

Cattle  Feeding."  The  Wolff  standard  was  used  unaltered 
until  1896,  when  as  a  result  of  further  experiments,  some 
alterations  were  made.  It  was  presented  annually  from 
1896  to  1906  by  Dr.  C.  Lehman,  under  the  name  of  the 
Wolff-Lehmann  Standards.  Table  XVI  gives  the  last  of 
these  standards. 

119.  Digestible  Nutrients.  The  term  digestible  nutrient 
is  applied  to  the  digestible  portion  of  feeds.  The  digestible 
nutrients  are  the  carbohydrates,  the  fats  and  protein. 

The  percentage  of  each  feed  that  is  digestible  is  deter- 
mined by  feeding  experiments  with  various  classes  of 
mature  animals.  Experiments  show  that  ruminants  digest 
the  same  kind  of  food  about  equally  well,  while  horses  and 
swine  digest  less  fiber  than  do  the  ruminants ;  however,  they 
seem  to  digest  the  concentrates  about  as  well  as  the  rumi- 
nants. Age  and  breed  seem  to  have  no  definite  influence  on 
digestion. 

120.  Metabolism.  MetaboHsm  is  the  process  by  which 
digested  nutrients  are  used  for  the  building  of  tissue  and 
by  which  these  tissues  are  broken  down  with  the  production 
of  heat.  The  building-up  processes  are  called  anabolism, 
while  the  breaking-down  processes  are  called  catabolism. 

The  digested  sugars  are  taken  up  by  the  capillaries 
and  carried  into  the  veins,  by  which  they  are  transferred  to 
the  liver,  where  they  are  made  into  glycogen  or  animal  starch 
and  stored  temporarily  as  such.  This  constitutes  the  ani- 
mal's reserve  supply  of  sugar,  for  it  is  reconverted  into  sugars 
and  made  use  of  by  the  animal  as  required,  especially  when 
work  is  being  done.  The  fats  seem  to  be  absorbed  as  soaps 
and  glycerin  into  the  intestinal  walls,  where  they  are 
converted  into  neutral  fats  and  find  their  way  into  the 
circulatory  .system.  The  products  of  the  protein  digestion 
are  absorbed  from  the  small  intestines  and  converted  into 
serum  albumin  and  serum  globulin,  which  are  the  nitrogenous 
materials  used  in  the  building  of  body  tissues.  All  of  these 
materials   are   transported   by   the   blood   to   the   various 


ANIMAL  NUTRITION 


177 


TABLE  XVL— THE  WOLFF-LEHMAN  FEEDING 

STANDARD 

Per  Dat  pek  1000 

LBS.  Live  Weight. 

Dry 
Mat- 
tor. 

Digestible  Nutrients. 

Crude 
Pro- 
tein. 

Carbo- 
hy- 
drates. 

Fat. 

Sum  of 
Nut-i- 
e.:  .. 

Nutri- 
tive 
Ratio, 
1. 

1.  Oxen: 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

At  rest  in  stall 

18 

0.7 

8.0 

0.1 

7.5 

11.8 

At  liffht  work 

22 

1.4 

10.0 

0.3 

9.7 

7.7 

At  medium  work. .  . 

25 

2.0 

11.5 

0.5 

12.0 

6.5 

At  heavy  work .... 

28 

2.8 

13.0 

0.8 

15.0 

5.3 

2.  Fattening  cattle: 

First  period 

30 

2.5 

15.0 

0.5 

15.6 

6.5 

Second  period 

30 

3.0 

14.5 

0.7 

17.0 

5.4 

Third  period 

26 

2.7 

15.0 

0.7 

17.2 

6.2 

3.  Milch  cows: 

When  yielding  daily 

ll.Olbs.  of  milk... 

25 

1.6 

10.0 

0.3 

10.2 

6.7 

16.6  lbs.  of  milk...  . 

27 

2.0 

11.0 

0.4 

12.2 

6.0 

22.0  lbs.  of  milk.. .  . 

29 

2.5 

13.0 

0.5 

14.4 

5.7 

27.5  lbs.  of  milk.... 

32 

3.3 

13.0 

0.8 

16.0 

4.5 

4.  Sheep: 

Coarse  wool 

20 

1.2 

10.5 

0.2 

9.1 

9.1 

Fine  wool 

23 

1.5 

12.0 

0.3 

10.5 

8.5 

5.  Breeding  ewes 

With  lambs 

25 

2.9 

15.0 

0.5 

16.3 

5.6 

6.  Fattening  sheep: 

First  period 

30 

3.0 

15.0 

0.5 

16.5 

5.4 

Second  period 

28 

3.5 

14.5 

0.6 

16.9 

4.5 

7.  Horses: 

Light  work 

20 

1.5 

9.5 

0.4 

10.0 

7.0 

Medium  work 

24 

2.0 

11.0 

0.6 

12.8 

6.2 

Heavy  work 

26 

2.5 

13.3 

0.8 

15.5 

6.0 

8.  Brood  sows 

22 

2.5 

15.5 

0.4 

19.0 

6.6 

9.  Fattening  swine: 

First  period 

36 

4.5 

25.0 

0.7 

31.2 

5.9 

Second  period 

32 

4.0 

24.0 

0.5 

29.2 

6.3 

Third  period 

25 

2.7 

18.0 

0.4 

22.0 

7.0 

178 


CHEMISTRY  OF  FARM  PRACTICE 
TABLE  XVI.— Continued 


10.  Growing  cattle: 
Dairy  breeds. 

Age  in       Av.  Live  Wt 
Months    per  Head,  Lbs 

2-3    150.... 

3-  6    300 

6-12    500 

12-18    700 

18-24    900 

11.  Grovoing  cattle: 

Beef  breeds. 

2-3         160 

3-6        330 

6-12        550 

12-18        750 

18-24        950 

12.  Growing  Sheep: 

Wool  breeds. 

4-6  60 

6-8  75.... 

8-11  80 

11-15  90 

15-20         100 

13.  Growing  sheep: 

Mutton  breeds. 

4-6  60 

6-8  80 

8-11         100 

11-15         120 

15-20         150 


Per  Day  per  1000  Lbs.  Live  Weight. 


Dry 

Mat- 
ter. 


Lbs. 

23 
24 
27 
26 
26 


23 
24 
25 
24 
24 


25 
25 
23 
22 

22 


26 
26 
24 
23 
22 


Digestible  Nutrients. 


Crude 
Pro- 
tein. 

Carbo- 
hy- 
drates. 

Fat. 

Sum  of 
Nutri- 
ents. 

Lbs. 

Lbs. 

Lbs. 

Lba. 

4.0 

13.0 

2.0 

21.0 

3.0 

12.8 

1.0 

17.0 

2.0 

12.5 

0.5 

13.7 

1.8 

12.5 

0.4 

12.8 

1.5 

12.0 

0.3 

11.8 

4.2 

13.0 

2.0 

21.5 

3.5 

12.8 

1.5 

19.0 

2.5 

13.2 

0.7 

15.8 

2.0 

12.5 

0.5 

13.9 

1.8 

12.0 

0.4 

13.2 

3.4 

15.4 

0.7 

18.4 

2.8 

13.8 

0.6 

15.8 

2.1 

11.5 

0.5 

12.8 

1.8 

11.2 

0.4 

12.0 

1.5 

10.8 

0.3 

11.0 

4.4 

15.5 

0.9 

20.9 

3.5 

15.0 

0.7 

17.8 

3.0 

14.3 

0.5 

16.3 

2.2 

12.6 

0.5 

13.8 

2.0 

12.0 

0.4 

12.8 

ANIMAL  NUTRITION 
TABLE  XYI.— Continued 


179 


Peb  Dat  per  1000  Lbs.  Live  Weight. 

Dry 
Mat- 
ter. 

Digestible  Nutrients. 

Crude 
Pro- 
tein. 

Carbo- 

hy- 
drates. 

Fat. 

Sum  of 
Nutri- 
ents. 

Nutri- 
tive 
Ratio, 
1. 

14.  Growing  swine: 

Breeding  stock. 

Age  in       Av.  Live  Wt. 
Months    per  Head,  Lbs. 

2-3          50 

3-5         100 

5-6         120 

6-8        200 

8-12        250 

15.  Growing,  faitening 

swine: 

2-3          50 

3-5         100 

5-  6         150 

6-  8        200 

9-12        300 

Lbs. 

44 
35 
32 
28 
25 

44 
35 
33 
30 
26 

Lbs. 
7.6 

4.8 
3.7 
2.8 
2.1 

7.6 
5.0 
4.3 
3.6 
3.0 

Lbs. 
28.0 
22.5 
21.3 
18.7 
15.3 

28.0 
23.1 
22.3 
20.5 
18.3 

Lbs. 
1.0 
0.7 
0.4 
0.3 
0.2 

1.0 

0.8 
0.6 
0.4 
0.3 

Lbs. 
38.0 

29.0 
26.0 
22.2 
17.9 

38.0 
30.0 
28.0 
25.1 
22.0 

4.0 

5.0 
6.0 
7.0 
7.5 

4.0 
5.0 
5.5 
6.0 
6.4 

tissues  nourishing  the  body  and  serve  as  a  source  of  heat 
and  energy. 

121.  Rations  for  Various  Purposes.  A  ration  is  the 
quantity  of  food  consumed  by  animals  per  1000  pounds  of 
Uve  weight  during  twenty-four  hours.  The  age  of  the 
animal  and  the  purpose  for  which  it  is  kept  exert  important 
influences  on  the  kind  and  amount  of  food  that  is  desirable. 

122.  Growth  Rations.  Young  and  growing  animals 
need  a  ration  that  will  produce  bone  and  muscle.  When 
maturity  is  reached,  there  is  little  subsequent  increase  in 
either  the  bones  or  the  muscles.  The  bones,  in  part,  and 
the  ligaments,  muscles,  nervous  system,  and  tendons  con- 
sist almost  entirely  of  protein,  therefore  the  young  and  grow- 


180  CHEMISTRY  OF  FARM  PRACTICE 

ing  animals  make  economical  use  of  large  amounts  of  pro- 
tein. It  is  not  desirable  to  feed  large  amounts  of  protein 
to  mature  animals  unless  they  are  either  pregnant,  or  giving 
milk,  or  producing  wool,  because  the  protein  eaten  above  the 
amount  needed  for  maintaining  the  body  tissues  is  un- 
economically  used. 

The  protein  of  the  milk  which  the  young  animal  takes  is 
very  largely  stored  in  the  body.  Soxhlet  found  that  72.6 
per  cent  of  the  protein,  96.6  per  cent  of  the  lime,  and  72.6 
per  cent  of  the  phosphorus  fed  in  the  milk  was  stored  in  the 
body  of  a  calf  between  two  and  three  weeks  old.  The 
proportion  stored  diminishes  as  the  animal  approaches 
maturity. 

Growing  animals  should  get  an  abundance  of  succulent, 
highly  nitrogenous  forage  plants.  These  plants  usually 
contain  a  liberal  amount  of  mineral  elements.  Some  con- 
centrate (such  as  bran,  meal,  oats)  is  usually  desirable  and 
an  abundant  supply  of  common  salt. 

123.  Maintenance  Rations.  A  certain  amount  of  food 
is  required  by  mature  animals  to  perform  the  body  functions, 
such  as  furnishing  heat  to  maintain  the  body  temperature, 
energy  to  perform  the  vital  functions,  and  various  materials 
to  replace  the  waste  tissue  that  is  constantly  being  broken 
down.  This  is  known  as  the  maintenance  ration.  If  it  is 
too  much  reduced,  starvation  will  result. 

These  rations  may  consist  largely  of  coarse  hay  and  straw 
or  "  roughages,"  as  they  are  called.  The  main  requirement 
is  the  production  of  heat,  and  roughages  contain  a  large 
amount  of  carbonaceous  material,  which  produces  heat  eco- 
nomically. Very  little  protein  is  required  in  the  maintenance 
ration,  because  protein  is  only  needed  for  the  replacement  of 
waste  tissue,  a  requirement  which  is  low  in  mature  animals. 

Experiments  have  shown  that  the  temperament  of  the 
animal,  the  condition  with  respect  to  flesh,  the  conditions 
under  which  the  animal  is  kept,  the  body  covering  and  the 
bodily  surface  exposed,  and  the  severity  of  the  weather  all 


ANIMAL  NUTRITION  181 

exert  influence  on  the  maintenance  ration  required.  As 
wide  a  nutritive  ratio  as  11.8  parts  of  digestive  carbohydrates 
to  one  part  of  digestive  protein  may  be  used  successfully 
for  a  maintenance  ration.  The  nutritive  ratio  is  deter- 
mined by  adding  2.25  times  the  digestible  fat  to  the 
digestible  carbohydrates,  and  dividing  by  the  digestible 
protein. 

124.  Fattening  Rations.  The  main  object  of  fattening 
is  to  improve  the  quality  of  the  meat;  the  accumulation  of 
fatty  tissue  is  a  secondary  object.  The  formation  of  fat 
and  its  accumulation  in  the  animal  is  governed  by  the  quan- 
tity and  quality  of  the  food  consumed  above  the  amount 
required  for  growth  and  maintenance.  It  is  difficult  to 
fatten  young  animals  on  account  of  their  tendency  to  make 
use  of  a  large  part  of  the  food  eaten  for  growth.  Exertion 
or  excitement  of  any  kind  lessens  the  amount  of  fat  formed 
from  a  given  quantity  of  feed.  The  fattening  ration  for 
beef  animals  depends  upon  their  condition  when  feeding  is 
begun.  If  the  animals  are  thin,  a  ratio  of  one  part  of  pro- 
tein to  six  parts  of  carbohydrate  is  recommended,  allow- 
ing a  liberal  amount  of  protein  during  the  first  period  of 
fattening,  in  order  that  the  muscular  tissues  may  be  built 
up.  From  12  to  15  pounds  of  digestible  nutrients  in  the  pro- 
portion already  mentioned  should  be  given  per  1000  pounds 
of  live-weight.  For  mature  animals  in  good  condition, 
a  nutritive  ratio  as  wide  as  1  to  10  or  12  is  suggested.  The 
nutritive  ratio  will  depend  to  some  extent  on  the  relative 
cost  of  feeds  containing  protein  to  the  cost  of  carbohydrate 
feeds.  In  the  Southern  States,  the  cheap  cottonseed  meal 
will  warrant  a  narrower  ration,  i.e.,  one  having  less  carbo- 
hydrate in  proportion  to  the  protein  than  is  usually  recom- 
mended elsewhere. 

Hogs  make  good  gains  on  a  narrower  nutritive  ratio  than 
is  needed  for  steers.  The  ratios  showing  best  results  range 
from  1  to  6  in  the  beginning  to  1  to  7  toward  the  end  of  the 
fattening  period.     It  has  been  shown  that  100  pounds  of 


182  CHEMISTRY  OF  FARM  PRACTICE 

dry  feed  consumed  will  form  6.2  pounds  of  increased  weight 
in  cattle,  8  pounds  in  sheep,  and  17.6  pounds  in  hogs.  An 
inspection  of  the  quotations  from  the  various  stock  markets 
will  show  that  on  this  basis  pork  is  the  most  profitable  meat 
to  produce. 

125.  Milk-Cows'  Ration.  The  Wolff-Lehmann  standards 
advise  for  milk-cows  a  nutritive  ratio  of  1  to  5.7  (i.e.,  digesti- 
ble protein  1  part,  digestible  carbohydrates+ (2.25  X  fat) 
=  5.7  parts).  For  a  cow  that  is  expected  to  give  22  quarts 
of  milk,  29  pounds  of  dry  matter  is  recommended  per  1000 
pounds  of  live-weight.  The  narrowest  ration  that  is  recom- 
mended in  these  standards  is  recommended  for  milk-cows. 
The  feed  of  a  dairy  cow  must  of  necessity  contain  a  consider- 
able amount  of  concentrates  which  are  high  in  price  compared 
with  roughages;  but  the  value  of  the  product  will  warrant 
the  increased  expenditure.  In  calculating  a  ration,  it  is 
not  always  practicable  to  get  the  exact  ratio  within  the 
prescribed  number  of  pounds  of  dry  matter.  If  possible, 
the  number  of  pounds  of  dry  matter  should  be  under  rather 
than  over  the  standard,  because  the  digestive  organs  of  a 
highly  specialized  animal  should  not  be  overtaxed.  The 
dairy  cow  is  essentially  a  machine  for  the  transformation 
of  feed  into  milk;  hence  every  effort  should  be  directed  to  a 
large  production  per  animal  so  as  to  reduce  the  cost  of  main- 
tenance rations  as  low  as  possible  by  having  fewer  animals 
to  maintain.  With  this  end  in  view,  the  dairy  cow,  when  in 
milk,  should  receive  an  abundant  supply  of  concentrates 
even  if  she  has  a  good  pasture.  While  dry,  she  can  be 
maintained  like  other  animals,  largely  on  roughage. 

126.  Ration  for  Work  Animals.  The  activity  of  the 
muscles  during  the  performance  of  work  greatly  increases  the 
amount  of  food  required  above  a  maintenance  ration.  It 
has  been  shown  by  repeated  experiments  that  energy 
is  derived  most  cheaply  through  the  oxidation  of  carbohy- 
drates and  fats  in  the  body;  that  a  sufficient  supply  of  car- 
bohydrates and  fats  is  an  adequate  source  for  all  the  energy 


ANIMAL  NUTRITION  183 

needed;  and  that,  if  these  are  insufficient,  the  protein  com- 
pounds' may  be  drawn  upon  as  a  source  of  energy.  This 
latter  source  makes  the  cost  of  the  energy  greater,  and  it 
also  imposes  extra  work  on  the  urinary  system,  through 
which  the  nitrogenous  products  of  the  oxidation  of  protein 
are  removed.  During  work,  the  quantity  of  carbon  dioxide 
exhaled  is  much  increased,  due  to  the  greater  quantity  of 
carbonaceous  matter  that  is  oxidized.  The  latest  investi- 
gations show  that  no  more  nitrogenous  tissue  is  broken 
down  by  animals  while  at  work  than  at  rest.  Working 
animals  thus  require  a  more  concentrated  feed  and  less 
roughage. 

The  horse  requires  considerably  less  dry  matter  per  1000 
pounds  of  live-weight  than  do  the  ruminants,  and  its  food 
should  be  rich  and  easily  digested.  Horses  must  be  fed  in 
accordance  with  the  work  that  they  are  doing,  the  ration 
being  reduced  when  at  rest  or  light  work,  to  secure  economical 
results.  It  is  advisable  to  give  most  of  the  roughage  at 
night.  A  moderate  but  not  an  excessive  amount  of  hay  is 
desirable.  The  Wolff-Lehmann  standards  recommend  a 
nutritive  ratio  of  1  to  6.2  for  a  horse  on  medium  work,  and 
Henry  states  that  "  from  10  to  18  pounds  of  concentrates 
should  be  fed,  according  to  the  severity  of  the  labor,  the 
total  grain  and  hay  averaging  not  less  than  2  pounds  per 
hundred  pounds  weight  of  the  animal." 


CHAPTER  XVIII 

FEEDS— THE    CALCULATION    OF   RATIONS 

A  BRIEF  discussion  of  some  of  the  more  commonly  used 
feeds  is  given  in  the  following  paragraphs : 

1.  The  Concentrate  Feeds — Cereals 

127.  Com.  Corn  is  essentially  a  carbonaceous  feed, 
and  is  not  as  good  for  growing  animals  as  is  oats.  Corn  has 
very  marked  heat-giving  and  fattening  properties  and,  for 
this  reason,  it  is  quite  extensively  used  for  fattening  steers, 
sheep  and  hogs.  It  is  highly  prized  as  a  feed  for  work  horses 
and  mules,  giving  most  satisfactory  results.  It  is  quite  use- 
ful for  making  up  a  part  of  the  carbohydrates  in  a  balanced 
ration. 

128.  Oats.  Oats  is  an  excellent  feed  for  stock,  because 
the  nutrients  are  present  in  a  good  ratio  for  the  work  horse, 
the  dairy  cow,  and  for  young  and  growing  animals.  Oats 
are  used  the  world  over  as  feed  for  horses,  giving  vigor  and 
stamina.  Ground  oats  have  been  found  superior  to  wheat 
bran  for  producing  both  milk  and  butter-fat.  The  protein 
contained  in  oats  shows  a  higher  coefficient  of  digestibihty 
than  that  of  corn,  while  the  carbohydrates  of  corn  show  a 
higher  digestibility  than  those  of  oats. 

129.  Barley.  Barley  is  used  for  a  stock  feed  mainly  on 
the  Pacific  slope,  where  it  flourishes  better  than  corn  or 
oats.  In  some  cases,  barley  is  injured  for  brewing  purposes 
by  bad  weather  at  harvest  time,  while  its  value  for  feeding 
purposes  is  unimpaired.  It  is  extensively  used  in  foreign 
countries  for  pork  production  and  for  the  feeding  of  dairy 
cows.     It  produces  pork  of  excellent  quality  and,   along 

184 


FEEDS— THE  CALCULATION  OF  RATIONS  185 

with  oats,  is  regarded  highly  as  a  feed  for  producing  milk  and 
butter  fat. 

130.  Dried  Brewers'  Grain.  Dried  brewers'  grain  is  a 
by-product  of  barley,  being  the  residue  left  from  brewing. 
In  brewing,  the  fermentable  carbohydrates  are  converted 
into  alcohol  and  the  protein,  fat,  and  crude  fiber  are  largely 
left  in  the  residue,  hence  dried  brewers'  grain  is  rich  in 
these  materials.  The  dry  matter  and  carbohydrates  of  the 
dried  brewers'  grain  are  lower  in  digestibility  than  the  same 
proximate  constituents  of  barley,  while,  on  the  other  hand, 
the  protein  and  fat  of  the  dried  brewers'  grain  are  more 
digestible  than  those  of  barley. 

131.  Rye.  Rye  is  not  keenly  reUshed  by  stock.  It 
is  subject,  also,  to  a  fungus  disease,  ergot,  that  may  be 
injurious. 

132.  Wheat.  Wheat,  on  account  of  its  cost  of  production 
and  its  value  as  a  human  food,  cannot  be  used  extensively 
for  feeding  stock.  When  fed  to  farm  animals,  it  is  best 
mixed  with  other  grains,  with  the  corn  for  work  stock  and 
with  oats  for  growing  stock. 

The  by-products  of  the  manufacture  of  wheat  into  flour — 
shorts,  middlings  and  bran — are  very  valuable  stock  feeds. 

Wheat  bran  is  the  outer  covering  of  the  wheat  kernel, 
and  is  that  part  which  is  first  removed  in  the  manufacture 
of  flour.  Its  volume  is  large  in  proportion  to  its  weight, 
therefore  it  is  often  used  to  give  bulk  to  a  feed  ration.  Bran 
contains  a  high  percentage  of  crude  protein  and  mineral 
matter.  It  is  an  excellent  feed  for  breeding  stock  of  all 
kinds,  for  horses,  and  for  dairy  cows.  It  serves  to  keep  the 
animal's  stomach  in  good  order  and  to  build  up  bone  and 
muscles  in  young  stock.  It  is  also  well  suited  for  use  in 
balancing  the  rations  of  dairy  cows. 

Wheat  middlings  are  composed  of  the  part  of  the  kernel 
below  the  bran.  It  is  even  higher  in  protein  content  than 
bran  and  is  an  excellent  material  to  form  a  part  of  the  ration 
of  hogs  and  dairy  cows. 


186  CHEMISTRY  OF  FARM  PRACTICE 

133.  Rice.  Rice  is  used  as  a  human  food  over  a  large 
part  of  the  world.  In  the  process  of  milling,  there  are 
several  by-products  which  are  of  value  as  stock  feed.  The 
rough  rice  is  put  through  a  machine  which  removes  the 
huU  and  leaves  the  rice  grain  intact.  The  grains  are  then 
rubbed  by  mechanical  means  until  the  skin  and  the  flour 
at  the  eye  of  grain  are  removed.  Some  grains  which  are 
inferior  are  so  abraded  that  they  grind  up.  The  material 
is  then  sifted  to  remove  the  flour,  and  the  fine  chaff  is  re- 
moved by  fanning.  This  chaff  is  then  mixed  with  the  flour, 
forming  what  is  known  as  rice  flour  or  hran. 

Rice  polish  is  obtained  by  the  operation  that  rubs  off 
the  last  covering  layer  and  a  good  part  of  the  starch.  This 
is  accomplished  mechanically  by  rubbing  the  rice  against 
pieces  of  moose  hide  or  sheepskin.  Rice  polish  contains  a 
considerable  amount  of  starch. 

Rice  meal  may  prove  injurious  to  the  intestines  of  hogs, 
on  account  of  the  irritation  caused  by  fine  splinters  of 
silicious  material  that  find  their  way  from  the  hulls  into  the 
meal. 

2.  Highly  Nitrogenous  Concentrates 

134.  Cottonseed  Meal.  Cottonseed  meal,  a  by-product 
of  the  cottonseed  oil  mills,  is  the  cheapest  source  of  digestible 
protein  that  can  be  bought  in  the  form  of  a  concentrate. 
On  this  account,  there  is  grave  danger  of  too  liberal  use  of 
it,  especially  in  the  Southern  States.  Where  used  in 
limited  quantities,  it  is  a  most  excellent  source  of  protein. 
Enough  cottonseed  hulls  to  reduce  the  nitrogen  to  about  the 
equivalent  of  7  per  cent  of  ammonia  is  often  added,  the 
crushers  claiming  that  this  promotes  a  more  complete 
removal  of  the  oil.  The  cottonseed  cake  used  for  domestic 
purposes  is  usually  ground  and  placed  in  100-pound  sacks, 
which  is  a  convenient  weight  for  handling.  Cottonseed 
meal  is  high  in  protein  and  fat,  but  low  in  digestible  carbo- 
hydrates. 


FEEDS— THE  CALCULATION  OF  RATIONS  187 

In  the  South  many  steers  are  fattened  on  cottonseed  meal 
as  the  sole  concentrate.  They  are  started  on  a  comparatively 
small  amomit,  about  3  or  4  pounds  per  day,  which  is  increased 
to  as  much  as  8  or  10  pounds  before  the  end  of  the  feeding 
period.  Cottonseed  meal  could  be  used  to  better  advantage 
as  a  part  of  the  ration,  some  concentrate  carrying  a  larger 
percentage  of  carbohydrates  being  substituted  as  the  other 
part;  The  excessive  feeding  of  cottonseed  meal  over  a  long 
period  of  time  has  led  to  harmful  effects;  in  some  cases 
blindness  and  partial  paralysis  are  induced,  but  no  such 
results  are  obtained  where  it  is  properly  mixed  with  other 
feeds. 

Cottonseed  meal  seems  to  vary  in  its  poisonous  qualities 
to  hogs,  some  meals  being  quite  toxic,  while  others  have  been 
fed  in  heavy  amounts  for  a  long  period  without  producing 
death.  Copperas  has  been  used  along  with  cottonseed  meal, 
as  an  antidote,  with  good  results.  The  feeder  should  real- 
ize that  in  feeding  cottonseed  meal  he  is  using  a  cheap 
feed  that  may  prove  injurious,  and  the  animals  should  be 
carefully  watched. 

Cottonseed  meal  may  be  fed  to  work  horses,  brood  mares, 
and  colts  in  limited  quantities  of  from  1  to  2  pounds  daily. 
It  gives  the  animals  a  good  coat,  and  is  keenly  reUshed  after 
they  learn  to  eat  it.  For  dairy  cows  the  use  of  cottonseed 
meal  to  an  amount  not  exceeding  5  pounds  per  1000  pounds 
of  live  weight  per  day  is  to  be  recommended.  Its  excessive 
use  has  a  tendency  to  raise  the  melting  point  of  the 
butter.  Cottonseed  meal  is  giving  good  results  as  a  poultry 
feed. 

135.  Linseed  Meal.  Linseed  meal  is  made  by  two  proc- 
esses. The  old-process  meal  is  the  residue  obtained  by 
expressing  the  oil  while  cold,  by  means  of  pressure.  New- 
process  meal  is  the  residue  of  the  extraction  of  the  oil  by 
means  of  naphtha,  which  is  later  driven  off  by  steam.  This 
cooking  makes  the  crude  protein  slightly  less  digestible. 
The  new  process  meal  contains  more  crude  protein,  but  only 


188  CHEMISTRY  OF  FARM  PRACTICE 

about  one-fourth  as  much  crude  fat,  the  new  process  being  a 
much  more  effective  means  of  removing  the  oil. 

Linseed  meal  may  be  fed  in  small  quantities  to  all  classes 
of  live  stock  with  excellent  results.  It  is  considerably- 
higher  in  price  than  cottonseed  meal,  and,  consequently, 
there  is  not  the  same  tendency  to  over-feed  it. 

136.  Meat  Scraps.  Meat  scraps,  or  tankage,  is  very 
high  in  protein.  In  buying  tankage  for  feeding,  care  should 
be  exercised  to  avoid  buying  acidulated  tankage.  Tankage 
is  rather  a  high-priced  source  of  nitrogenous  feed.  It  has 
been  used  for  cattle,  sheep,  hogs,  and  horses  with  good 
results.  Parts  from  diseased  animals  are  often  incorporated 
in  tankage,  and  infection  from  this  source  is  possible,  though 
improbable;  not  a  case  of  such  infection  has  been  reported 
by  any  Station  experimenting  with  this  feed.  In  prep- 
aration, the  tankage  is  cooked  by  means  of  steam  under 
pressure  to  facilitate  the  removal  of  the  grease.  This 
treatment  should  produce  a  sterile  condition.  This  form 
of  protein  does  not  seem  to  have  its  digestibility  harmfully 
influenced  because  of  the  cooking,  for  the  protein  is  given 
as  93  per  cent  digestible.  Tankage  is  highly  prized  as  a 
poultry  feed. 

137.  Dried  Fish.  Dried  fish  has  been  used  to  some 
extent  as  a  feed  for  dairy  cows  without  any  harmful  or 
objectionable  influence  on  the  quality  of  the  milk.  It  is 
highly  nitrogenous,  containing  as  high  as  48  per  cent  of  pro- 
tein as  well  as  a  high  percentage  of  fat,  both  of  which  are 
highly  digestible.  In  the  table  of  digestibility  the  protein 
is  given  as  93  per  cent  digestible  and  the  fat  as  98  per  cent. 

138.  Blood  Meal.  Blood  meal  is  the  richest  available 
source  of  protein,  and  contains  about  84  per  cent,  of  which 
84  per  cent  is  digestible.  It  has  given  good  results  when 
fed  to  hardworked  horses  at  the  rate  of  about  1  pound  per 
day,  and  when  fed  to  sickly  calves  in  their  milk  at  the  rate 
of  from  a  teaspoonful  to  a  tablespoonful.  When  fed  to 
pigs,  1  pound  of  blood  meal  may  replace  12  pounds  of  skim 


FEEDS— THE  CALCULATION  OF  RATIONS  189 

milk  if  mixed  with  some  material  that  the  pigs  will  eat,  and, 
for  lambs  ^  pound  of  blood  meal  may  be  fed  per  100  pounds 
of  hve  weight  with  good  results. 

139.  Soybean  Meal.  Soybean  meal  is  highly  nitrogen- 
ous, containing  about  33.5  per  cent  of  protein  which  shows 
a  digestibility  of  87  per  cent.  It  forms  a  better  feed  after 
the  oil  is  expressed  than  when  the  whole  bean  is  ground  and 
fed. 

140.  Peanuts.  Peanuts  run  high  in  both  protein  and  fat, 
and  form  an  excellent  source  of  feed  for  hogs.  Peanuts 
yield  about  40  bushels  per  acre,  and  are  best  harvested  by 
the  hogs.  Unless  the  fattening  is  completed  by  feeding 
corn,  the  lard  will  not  solidify  at  ordinary  temperatures. 
When  the  oil  is  extracted,  the  peanut  meal  may  be  used  to 
some  Qxtent  as  a  feed  for  stock.  This  meal  contains  the 
highest  protein  content  of  any  vegetable  material — ^about 
47  per  cent. 

3.  The  Roughages 

141.  Timothy.  Timothy  is  the  most  popular  hay  for 
city  markets,  and  serves  well  as  a  roughage  along  with  such  a 
concentrate  as  oats;  but  under  farm  conditions  other  hays 
are  more  cheaply  grown,  because  they  yield  more  heavily. 
The  early  cut  timothy  hay  contains  more  protein  in  propor- 
tion to  the  carbohydrates  present,  and  therefore  is  well 
suited  to  the  requirements  of  dairy  cows  and  young  and 
growing  stock.  The  late  cut  hay  is  better  for  horses  and  for 
fattening  cattle.  Late  cutting  also  gives  a  better  yield.  On 
account  of  its  quality,  timothy  is  highly  valued  for  horses, 
but  it  does  not  contain  a  large  amount  of  digestible  nutrients. 
Timothy  is  not  an  economical  feed  for  fattening  cattle  nor 
for  dairy  cows;  in  fact,  it  is  most  valuable  as  a  roughage  for 
driving,  saddle,  and  race  horses.  From  the  farmer's  view- 
point, the  chief  value  of  timothy  lies  in  the  fact  that  it  is  an 
easily  marketed  hay. 

142.  Cereals.     The  cereals  are  used  to  some  extent  as 


190  CHEMISTRY  OF  FARM  PRACTICE 

roughages,  and  even  where  they  are  harvested  and  threshed, 
the  straw  has  some  value  as  roughage. 

Oat  straw  is  the  most  nutritious  of  the  straws,  and  may  be 
used  to  advantage  as  a  part  of  a  maintenance  ration. 

Oat  hay  is  easily  grown,  and  is  much  rehshed  by  stock. 
The  time  of  cutting  should  be  decided  to  some  extent  by  the 
stock  for  which  it  is  to  be  used.  The  protein  content  in- 
creases until  early  in  the  milk  stage  of  growth,  when  the  hay 
should  be  cut,  if  a  maximum  protein  content  is  desired.  Most 
of  the  starch  in  oats  is  formed  after  the  beginning  of  the  milk 
stage ;  hence,  if  a  feed  high  in  nitrogen-free  extract  is  desired, 
the  cutting  should  be  delayed  as  long  as  possible,  for  there 
is  a  rapid  increase  in  the  total  dry  matter  of  about  40  per 
cent  from  the  early  milk  stage  to  maturity,  the  combined 
starch  and  sugars  increasing  at  this  time  from  about  13  to 
30  per  cent.  For  dairy  cows  and  young  and  growing  stock, 
the  early  cutting  would  be  advisable.  For  feeding  along 
with  highly  nitrogenous  feeds,  the  later  cutting  will  be  best. 

143.  Legumes.  The  legumes  should  be  grown  and  used 
for  roughage  as  much  as  possible  on  account  of  their  beneficial 
influence  on  the  soil,  in  addition  to  their  high  content  of 
digestible  nutrients. 

Alfalfa  hay  is  especially  valuable  for  practically  all 
classes  of  stock.  It  is  excellent  for  dairy  cows  and  fattening 
steers.  For  dairy  cows  it  may  be  used  as  a  substitute  for  a 
small  part  of  the  concentrate,  yielding  cheaper  milk;  while 
in  fattening  beef  cattle  it  may  be  used  to  a  larger  extent 
in  replacing  the  concentrates.  It  has  an  especial  value  as 
a  maintenance  ration  for  young  hogs,  and  can  be  used  to 
some  extent  for  fattening  hogs.  Sheep  thrive  on  alfalfa 
hay.  Work  horses  can  use  it  to  good  advantage,  but  it  is 
not  advisable  to  feed  it  to  driving  horses. 

Red  clover  is  much  used  in  rotations  in  the  Northern  part 
of  the  United  States.  When  well  cured  red  clover  hay  is 
a  desirable  feed  for  horses.  Experiments  show  that  it  gives 
splendid  results  for  fattening  beef  cattle,  both  by  reducing  the 


FEEDS— THE  CALCULATION  OF  RATIONS  191 

amount  of  concentrates  necessary  and  by  shortening  the 
feeding  period.  For  dairy  cows,  clover  hay  is  a  splendid 
roughage,  being  rich  in  protein  and  in  mineral  elements.  It 
is  excellent  for  young  stock  on  account  of  its  high  content  of 
bone-  and  muscle-producing  materials.  Clover  is  especially 
valuable  as  a  feed  for  hogs. 

Crimson  clover  makes  a  hay  of  fair  quality  when  cut  early; 
if  cut  late,  the  blossoms  are  covered  with  very  small  barbed 
heads  which  may  accumulate  in  spherical  balls  in  the  stom- 
achs of  horses,  and  in  some  cases  may  stop  up  the  intestines 
so  that  death  may  ensue. 

Japanese  clover  on  rich  land  yields  a  hay  of  good  quality. 

Canadian  field  peas  or  common  field  peas  are  grown  in  the 
Northern  States  along  with  oats  for  hay.  This  hay  is  both 
nutritious  and  keenly  relished  and  fills  very  much  the  same 
place  in  the  North  as  oats  and  vetch  do  in  the  South. 

Cowpea  vines  are  harvested  for  hay  in  the  Southern  States. 
The  vines  should  be  cut  about  the  time  that  the  first  pods 
begin  to  ripen,  in  order  that  a  large  yield  may  be  secured 
and  that  the  leaves  may  be  cured  along  with  the  vines.  It 
has  been  found  that  the  leaves  make  up  about  30  per  cent  of 
the  weight  of  the  hay  and  that  they  are  much  richer  in  pro- 
tein than  are  the  stems.  Cowpea  hay  can  be  successfully 
substituted  for  a  part  of  the  concentrate  for  dairy  cows  and 
for  fattening  steers.  It  can  be  used  for  a  maintenance 
ration  for  mules  on  Southern  farms  during  the  winter 
months  when  they  are  not  at  work. 

Hairy  vetch  is  adapted  to  a  large  part  of  the  United 
States  and  makes  a  comparatively  easily  cured  and  nutri- 
tious hay.  It  should  be  sowed  along  with  a  cereal  to  support 
the  vines.  In  the  South  these  fields  furnish  good  pasturage 
during  the  winter  months  when  the  land  is  dry  enough 
for  animals  to  walk  on  it. 

Soybeans  are  planted  for  a  hay  crop  to  some  extent,  and 
the  cured  vines  yield  a  nutritious  hay,  which  can  be  pro- 
duced at  a  low  cost.     Soybeans  are  more  erect  in  their 


192 


CHEMISTRY  OF  FARM  PRACTICE 


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FEEDS— THE  CALCULATION  OF  RATIONS 


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194  CHEMISTRY  OF  FARM  PRACTICE 

habit  of  growth  than  the  running  varieties  of  cowpeas; 
consequently,  they  are  more  easily  cut  and  harvested.  The 
Tennessee  Station  has  obtained  good  results  from  feeding 
soybean  hay  to  dairy  cows;  in  fact,  it  proved  superior  to 
alfalfa  hay. 

144.  Composition  and  Digestibility  of  Feeds.  Table 
XVII,  which  is  compiled  largely  from  Henry's  "  Feeds  and 
Feeding,"  shows  the  composition  and  digestibiUty  of  a  num- 
ber of  feeding  stuffs. 

145.  The  Calculation  of  Rations.  The  data  of  Table 
XVII  and  that  given  in  the  preceding  chapter  furnish  all 
the  information  that  is  necessary  for  the  calculation  of 
balanced  rations.  Two  concrete  examples  are  here  given 
to  show  the  method  and  the  operations  involved  in  such 
calculations. 

Example  1.  The  single  feed,  oats,  is  nearly  a  balanced 
ration  for  horses;  its  nutritive  ratio  is  therefore  calculated  as 
the  simplest  illustration. 

The  Wolff-Lehmann  standard  shows  that  a  ration  for  a 
horse  consists  of  24  pounds  of  dry  matter.  From  Table 
XVII  we  find  that  89.6  per  cent  of  oats  is  dry  matter. 
Hence,  24X100-^89.6  =  26.8  pounds,  or  26.8  pounds  of 
oats  must  be  fed  to  furnish  24  pounds  of  dry  matter.  There- 
fore, calculating  the  nutritive  ratio  of  26.8  lbs,  of  oats,  we 
have  the  values  shown  in  Table  XVIII. 

In  the  calculation,  the  pounds  of  feed  are  multiplied  by 
the  percentage  of  each  nutrient  and  the  result  is  given  in 
the  third  column  of  the  table.  This  result  is  then  multiplied 
by  the  coefficient  of  digestibility,  or  per  cent  of  digestible 
material,  and  the  amount  of  digestible  nutrients  are  placed 
in  each  case  under  the  proper  head  in  the  table.  The  diges- 
tible carbohydrates  are  added  to  2.25  times  the  digestible 
fat  (because  fat  is  estimated  to  have  2.25  times  the  heat- 
giving  power  of  carbohydrates)  and  the  sum  is  divided  by 
the  digestible  protein.  The  quotient  gives  the  nutritive 
ratio  compared  with  the  digestible  protein  as  the  unit. 


FEEDS— THE  CALCULATION  OF  RATIONS 


195 


TABLE  XVIII.— THE  NUTRITIVE  RATIO  OF  26.8  POUNDS  OF 

OATS 


Digestible  Nutrients. 

a 

,   e« 

o"** 

Nutrient. 

o 
H 

"o 

(6 

.S 

SO 

(5 

a 

o 

a 
o 

■*^ 
03 
kl 

>> 

>-^ 

O 

S 

<0 

-a 

o 

ki 

o 

b 

a 

e^ 

■s 

5^5 

(2* 

z 

P4 

w 

O 

O 

(^ 

2: 

Dry  matter 

89  6 

24.0 

24  0 

Crude  protein 

11   4 

3.05 

77 

?  35 

Crude  fiber 

10.8 
59.4 

2.89 
15.92 

31 

77 

0.90 
12.26 

Nitrogen-free  extract. .  .  . 

Fat 

4.8 

1.29 

89 

1.15 

Ration 

24.0 
24.0 

2.35 
2.0 

13.16 
11.0 

1.15 
0.6 

1:6.7 

Wolff-Lehmann 

1:6.2 

Thus  in  this  case,  -— -  X  26 . 8  pounds  =  24  pounds,  the 


amount  of  dry  matter; 


100 
11.4 


100 


X  26 . 8  =  3 .  05  pounds  protein, 


etc.  Of  this  protein,  77  per  cent  or  yV^  is  digestible ;  hence 
tVoX3.05  pounds  =  2. 35  pounds  digestible  protein,  simi- 
larly, xVoX2.89  pounds  =  0.90  pound  digestible  crude 
fiber,  etc.,  etc.  The  nutritive  ra^io  =  digestible  protein: 
(digestible  carbohydrates  +  2.25  X  fat)  =  2.35  :  (0.90 
+  12. 26+2. 25X1. 15)  =  1  :  6.7. 

The  foregoing  calculation  shows  that  oats  contain  a 
nutritive  ratio  well  suited  to  the  needs  of  the  horse,  but 
that  the  proper  amount  of  digestible  dry  matter  contains 
too  large  an  amount  of  nutrients;  therefore,  even  with  oats, 
some  hay  should  be  fed  to  give  bulk.  When  this  is  done, 
the  amount  of  oats  fed  will  be  reduced. 

Example  2.     The  calculation  of  a  ration  for  a  dairy 

,  |!ow  giving  27.5  pounds  of  milk  will  serve  as  an  example  of 

a  more  complicated  problem.     Suppose  that  it  is  proposed 


196 


CHEMISTRY  OF  FARM  PRACTICE 


to  feed  4  pounds  of  cottonseed  meal,  6  pounds  of  wheat 
bran,  10  pounds  of  alfalfa  hay,  and  40  pounds  of  silage; 
the  results  based  on  the  percentages  given  in  table  XVII 
and  calculated  as  in  Example  1,  are  tabulated  in  table  XIX. 


TABLE  XIX.— AN  UNCORRECTED  RATION 


Lbs. 

as 

Fed. 

Dry 
Matter. 

DiGESTiBLi;  Nutrients. 

Pro- 
tein. 

Fiber 

and 

N-Free 

Ext. 

Fat. 

Nutri- 
tive 
Ratio. 

Cottonseed  meal. .  . 

Wheat  bran 

Alfalfa  hay 

Corn  silage 

4.0 

6.0 
10.0 
40. 

3.72 

5.29 

9.34 

10.56 

1.28 

0.71 
1.14 
0.56 

0.15 
0.76 
0.22 
2.29 
1.35 
2.58 
1.59 
3.87 

0.39 
0.15 
0.08 
0.28 

Total 

Wolff-Lehmann .  .  . 
(From  Table  XVI.) 

60.0 

28.91 
32.00 

-  3.09 

3.69 
3.30 

+0.39 

12.81 
13.00 

-  0.19 

0.90 
0.80 

+0.10 

1:4 
1:4.5 

An  inspection  of  the  results  in  Table  XIX  shows  that  the 
protein  content  is  more  than  is  required,  while  the  fat  and 
carbohydrates  are  about  right  in  amount.  It  is  desirable  to 
keep  the  total  dry  matter  lower,  if  possible,  than  the  Wolff- 
Lehmann  figure.  The  correction  of  this  ration  can  be 
accomplished  by  reducing  the  cottonseed  meal  and  increasing 
the  bran  or  by  reducing  the  alfalfa  hay  and  substituting  a 
hay  cheaper  and  less  nutritious.  In  sections  where  cotton- 
seed meal  is  cheap,  its  reduction  will  not  be  desirable;  but, 
in  sections  where  it  is  expensive,  1|  pounds  of  it  may  be 
replaced  with  an  equal  weight  of  corn  meal.  Table  XX 
shows  such  a  correction. 


FEEDS— THE  CALCULATION  OF  RATIONS 


197 


TABLE  XX.— A  CORRECTED  RATION  FOR  A  DAIRY  COW 
PRODUCING  27.5  LBS    OF  MILK 


Pounds. 

Digestible  Ndtkients. 

1 

Feed. 

Dry 
Matter. 

Pro- 
tein. 

Fiber 
and 

N-Free 
Ext. 

Fat. 

Nutri- 
tive 
Ratio. 

Cottonseed  meal. .  . 

Corn  meal 

Wheat  bran 

Alfalfa  hay 

Corn  silage 

2.5 
1.5 
6.0 

10.0 

43.0 

2.33 
1.28 
5.29 

9.34 

10.56 

0.80 
0.09 
0.71 

1.14 

0.56 

f      0.06 
1     0.48 
0.95 
0.22 
2.29 
1.35 
2.58 
1.59 
[     3.87 

0.24 
0.05 
0.15 

0.08 

0.28 

Totals 

60.0 

28.80 
32.00 

-  3.20 

3.30 
3.30 

+    .00 

13.39 
13.00 

+  0.39 

0.80 
0.80 

+    .00 

1:4.6 

Wolff -Lehmann .  .  . 
(From  Table  XVI.) 

1:4.5 

The  substitution  of  corn  meal  in  place  of  1^  pounds  of 
the  cottonseed  meal  served  to  balance  the  ration  very 
satisfactorily. 

These  type  calculations,  problems  1  and  2,  show  the  steps 
involved  in  calculating  rations.  Considerable  liberty  may 
be  taken  with  the  nutritive  ratios  in  order  to  use  cheap  feeds, 
but  they  serve  as  a  guide  and  should  be  followed  as  closely 
as  possible  for  best  results. 


CHAPTER  XIX 

MILK  AND  ITS  PRODUCTS 

146.  Milk.  Milk  contains  water,  fat,  casein,  albumin, 
milk-sugar,  and  mineral  salts  in  proportions  especially 
suited  to  the  young  of  the  mammal  producing  it.  Table 
XXI  shows  the  average  composition  of  the  milk  of  a  num- 
ber of  mammals : 

TABLE  XXL— THE  COMPOSITION  OF  VARIOUS  MILKS 


Mammal. 

Per  Cent 

of 
Water. 

Per  Cent 

of  Total 

Solids. 

Per  Cent 

of 
Proteids. 

Per  Cent 

of 

Fat. 

Per  Cent 

of 

Sugar. 

Per  Cent 

of 

Ash. 

Human 

88.00 

87.25 
86.60 
81.30 
90.00 
89.60 
67.80 
41.10 

12.00 
12.75 
13.40 
18.70 
10.00 
10.40 
32.20 
58.90 

1.50 

3.50 
4.60 
6.30 
1.90 
2.20 
3.10 
11.20 

3.50 
4.00 

4.30 
6.80 
1.10 
1.60 
19.60 
45.80 

6.80 

4.50 
4.00 
4.80 
6.70 
6.10 
8.80 
1.30 

0.20 

Cow   

0.75 

Goat 

0.60 

Ewe 

0.80 

Mare 

0.30 

Ass 

0.50 

Elephant 

0.70 

Porpoise 

0.60 

147.  Milk    from    Different    Breeds    of    Cattle.    The 

nutritive  ingredients  of  milk  are  combined  in  such  propor- 
tions that  it  serves  excellently  as  a  part  of  the  diet  of  adults, 
and  its  products,  butter  and  cheese,  are  widely  used  and 
highly  nutritious  foods.  For  the  production  of  butter,  the 
content  of  fat  in  the  milk  is  of  prime  importance,  provided 
that  the  yield  of  milk  is  not  sacrificed  to  this  end.  In  table 
XXII  are  shown  the  differences  in  composition  of  milk  of 
different  breeds  of  cattle. 

198 


MILK  AND  ITS  PRODUCTS 


199 


TABLE  XXII.— A  COMPARISON  OF  THE  COMPOSITION  OF 
MILK   FROM   DIFFERENT   BREEDS 


Breed. 

Per  Cent 

of 
Water. 

Per  Cent 
of  Total 
Solids. 

Per  Cent 

of 
Proteins. 

Per  Cent 

of 

Fat. 

Per  Cent 

of 
Sugar. 

Per  Cent 

of 

Ash. 

Jerseys 

85  .'66 

87.55 
87.88 

14.34 
12.45 
12.12 

3.96 

3.27 
3.28 

4.78 
3.65 
3.51 

4.85 
4.80 
4.69 

0.75 

Shorthorns 

Holstein-Friesians  . 

0.73 
0.64 

The  Jersey  breed  is  noted  for  the  production  of  rich 
milk,  cream,  and  butter.  The  Holstein-Friesian  breed  is 
highly  specialized  for  the  production  of  a  large  quantity  of 
milk.  This  milk  serves  well  for  the  manufacture  of  cheese, 
and  where  the  per  cent  of  fat  meets  city  inspection  require- 
ments, a  dairy  of  this  breed  will  prove  especially  profitable 
on  account  of  the  large  yield  of  milk.  The  n  ilking  strains 
of  the  Shorthorn  breed  are  desirable  both  for  the  production 
of  the  home  milk  supply  in  rural  districts  and  as  beef  animals. 

148.  Danger  from  Infected  Milk.  Before  being  used 
for  feeding  infants,  cows'  milk  must  be  changed  in  com- 
position to  make  it  more  nearly  conform  to  the  composition 
of  human  milk.  This  is  accomplished  by  diluting  it  with 
water  to  reduce  the  protein  and  fat  and  by  adding  sugar. 

Great  care  should  be  taken  with  the  milk  used  for  chil- 
dren. It  is  estimated  that  500,000  deaths  occur  annually 
in  the  United  States  from  diseases  and  derangements  due 
to  infected  or  bad  milk.  Milk  is  an  excellent  medium  for 
the  growth  of  harmful  bacteria,  and  every  precaution  should 
be  taken  to  assure  its  purity.  Where  milk  is  purchased, 
there  is  danger  from  watering,  leading  to  a  lowering  of  its 
nutritive  value,  and  from  preservatives.  Even  when  pro- 
duced at  home,  every  care  should  be  exercised  to  see  that 
the  cows  are  healthy  and  that  no  poisonous  weeds  are  fed. 
Any  unusual  appearance  or  odor  of  milk  should  be  regarded 
with  suspicion. 

An  abnormal  color  in  milk  is  easily  noticeable.    Blue  color 


200 


CHEMISTRY  OF  FARM  PRACTICE 


may  be  due  to  microorganisms;  yellow  color  to  chromogenic 
organisms  or  to  the  fact  that  rhubarb  has  been  eaten; 
red  color  to  the  eating  of  rhubarb,  madder,  and  also  to  several 


groups  of  bacteria,  and  green  color  is  caused  by  pus-forming 
bacteria.  Any  unusual  color  is  to  be  regarded  with  instant 
suspicion,  and  such  milk  should  not  be  used  until  the  source 
and  harmless  character  of  the  color  is  established. 


MILK  AND  ITS  PRODUCTS  201 

Typhoid  fever,  scarlet  fever,  diphtheria,  foot  and  mouth 
disease,  cowpox,  anthrax,  and  glandular  tuberculosis  are 
some  of  the  forms  of  diseases  that  are  known  to  be  occasioned 
by  the  use  of  infected  milk. 

Milk  is  so  liable  to  become  a  source  of  danger  as  a  food 
that  all  well-governed  cities  have  placed  the  milk  supply 
under  government  inspection.  In  many  cases  this  control 
is  so  efficient  that  milk  obtained  in  the  city  is  safer  and  better 
than  that  obtained  in  the  country.  To  pass  the  inspection 
the  farmer  is  compelled  to  deliver  a  purer  and  higher  grade 
of  milk  for  city  markets.  The  New  York  Board  of  Health 
have  ruled  that  milk  containing  more  than  88.5  per  cent 
of  water  or  less  than  3  per  cent  of  fat  or  less  than  11.5 
per  cent  of  solids  cannot  be  offered  for  sale  legally  in  that  city. 
The  Boston  Board  of  Health  prohibits  the  sale  of  milk  con- 
taining more  than  500,000  bacteria  per  cubic  centimeter  or 
which  is  delivered  at  a  temperature  higher  than  50"  F. 

149.  Preservatives.  Milk  becomes  infected  a  short  time 
after  production.  If  the  use  of  the  milk  as  a  food  is  delayed, 
bacteria  increase  to  inconceivable  numbers.  At  the  temper- 
ature of  the  human  body  (98.6°  F.  or  36°  C.)  one  bacterium 
in  milk  will  multiply  to  75,000  in  twenty-four  hours.  If  the 
temperature  is  reduced  to  50°  F.  bacteria  will  increase  very 
slowly,  if  at  all.  All  bacteria  are  not  dangerous;  some 
species  are  friendly,  aiding  in  the  processes  of  digestion  and 
assimilation.  There  are  three  ways  of  controlKng  the  num- 
ber of  bacteria:  First,  by  preventing  as  far  as  possible 
infection,  by  healthy  cows,  cleanly  methods  of  production 
and  handling  and  control  of  temperature;  second,  by  treat- 
ing the  milk  by  steriUzation  or  pasteurization  and  then  guard- 
ing against  further  infection;  third,  by  adding  to  the  milk 
some  preservative  which  is  germicidal.  The  last  of  these 
methods  is  to  be  condemned.  Some  preservatives  are 
harmful,  and  all  serve  to  preserve  the  milk  by  producing  con- 
ditions that  are  not  conducive  to  easy  digestion.  Formalin, 
which  is  a  40  per  cent  solution  of  formaldehyde  (HCHO), 


202 


CHEMISTRY  OF  FARM  PRACTICE 


is  used  in  proportions  of  from  1  part  forrrialin,  20,000  parts 
milk  or  to  50,000  parts  milk,  the  smaller  quantity  will 
preserve  milk  for  two  days.     Sodium  carbonate  (Na2C03) 


a 


and  magnesium  carbonate  (MgCOs)  serve  to  neutralize 
acidity  and  to  improve  the  appearance  of  the  milk.  Potas- 
sium carbonate  (K2CO3),  borax  (Na2B407)  and  boracic  add 
(H3BO3)  are-  used  as  preservatives.    They  tend,  however, 


MILK  AND  ITS  PRODUCTS  203 

to  retard  the  separation  of  the  cream.  Sodium  henzoate 
(CGHsCOONa),  salicylic  acid  (C6H4OHCOOH),  potassium 
nitrate  (KNO3),  calcium  peroxide  (Ca02)  and  hydrogen 
peroxide  (H2O2)  in  milk  are  all  harmful.  The  fluorides, 
fluosilicates  and  fluoborates  are  dangerous  poisons.  Milk 
that  is  properly  produced  will  keep  as  long  as  is  necessary 
without  preservatives,  and  the  use  of  preservatives  but 
serves  to  hide  filthy  handling  and  bad  management. 

The  pasteurization  of  milk  consists  in  keeping  it  at  a 
temperature  between  63°  C.  and  75°  for  at  least  twenty  min- 
utes, then  rapidly  chilhng  the  milk.  The  necessity  for 
pasteurizing  milk  should  be  avoided,  because  lecithin,  which 
is  beneficial  to  growing  children,  is  destroyed,  and  also 
because  enzymes  which  are  helpful  to  digestion  are  killed. 
Pasteurization  serves  to  kill  disease-producing  bacteria 
when  present.  Imperfect  pasteurization  of  milk  is,  how- 
ever, a  source  of  danger,  because  incomplete  heating  kills 
the  harmless  lactic  acid  bacteria,  while  the  dangerous  putre- 
factive bacteria  may  not  be  affected.  Such  milk  will  keep 
from  souring  for  a  long  time,  and  so  the  buyer,  deceived  by 
the  absence  of  souring,  may  use  milk  impregnated  with  dis- 
ease-producing germs. 

150.  The  Detection  of  Formaldehyde  in  Milk.  The  pres- 
ence of  formaldehyde  in  milk  may  be  detected  as  follows: 

Method  1:  Sulphuric  Acid  Test:  Place  5  to  10  cubic 
centimeters  of  the  milk  in  a  large  test-tube,  or  clean  bottle, 
and  add  one-half  the  amount  of  commercial  sulphuric  acid, 
carefully  pouring  the  acid  down  the  side  of  the  tube  or  bottle 
so  that  the  milk  and  acid  are  not  mixed.  As  the  acid  is 
heavier  than  the  milk,  it  will  sink  to  the  bottom  of  the  vessel. 
If  a  violet  zone  is  formed  at  the  junction  of  the  two  liquids, 
formaldehyde  is  present.  The  sulphuric  acid  should 
contain  some  iron;  if  chemically  pure  acid  is  used,  a  little 
ferric  chloride  must  be  added. 

Method  2:  Hydrochloric  Acid  Test.  First  prepare  the 
acid  for  the  test  by  adding  two  drops  of  ferric  chloride 


204  CHEMISTRY  OF  FARM  PRACTICE 

solution  to  50  cubic  centimeters  of  the  concentrated  acid 
(sp.  gr.  1.20).  Place  10  cubic  centimeters  of  the  milk  in 
a  casserole  or  a  porcelain  evaporating  dish,  add  an  equal 
volume  of  the  prepared  acid  and  heat  the  mixture  nearly 
to  boiling.  While  heating,  swirl  the  contents  of  the  dish 
gently  so  as  to  break  up  the  curd. 

The  presence  of  formaldehyde  is  indicated  by  a  violet 
color  varying  in  intensity  with  the  amount  of  formaldehyde 
present.  If  no  lormaldehyde  is  present,  the  mixture  turns 
brown. 

151.  Detection  of  Boracic  Acid.  To  10  cubic  centimeters 
of  the  milk  add  6  drops  of  concentrated  hydrochloric  acid 
and  mix  thoroughly.  Dip  a  strip  of  turmeric  paper  in  the 
mixture  and  dry  the  paper  by  wrapping  it  about  a  test-tube 
which  contains  boiling  water.  In  the  presence  of  boracic 
acid  or  a  borate  the  turmeric  paper,  which  is  a  reddish-brown 
color,  will  turn  to  a  greenish-black  color  upon  treatment 
with  a  drop  of  sodium  hydroxide. 

152.  Testing  Milk  for  Per  Cent  of  Fat.  The  Babcock 
test  is  a  rapid,  accurate,  and  inexpensive  method  for  deter- 
mining the  amount  of  fat  in  milk  and  other  dairy  products. 

For  making  the  test,  a  centrifuge,  two  forms  of  which  are 
shown  in  Fig.  67  and  the  test  bottles,  pipette  for  measuring 
the  milk,  acid  measure,  brush  for  cleaning  the  bottles,  and 
sulphuric  acid,  shown  in  Fig.  68,  are  required. 

The  neck  of  the  test  bottles  are  marked  with  a  graduated 
scale,  each  small  division  representing  two-tenths  of  1 
per  cent  of  fat.  Every  fifth  division  is  a  long  one  and  repre- 
sents 1  per  cent.  In  making  the  test  17.5  cubic  centimeters 
of  milk,  which  weigh  18  grams,  are  first  slowly  run  into  the 
bottle  by  means  of  the  pipette,  holding  the  pipette  at  an 
angle  as  is  shown  in  Fig.  69.  This  method  of  running  in  the 
milk  prevents  overflowing  due  to  the  stopping  of  the  outlet 
for  air. 

The  reason  for  the  use  of  18  grams  of  milk  is  that  the  neck 
of  the  test  bottle  is  graduated  to  hold  just  2  cubic  centi- 


MILK  AND  ITS  PRODUCTS 


205 


Fig.  67. — Centrifuge  for  the  Babcock  test. 


Fig.  68. — Additional  apparatus  for  the  Babcock  test. 


206  CHEMISTRY  OF  FARM  PRACTICE 

meters  in  the  graduated  portion.  The  specific  gravity  of 
milk  fat  is  0.90,  therefore  the  amount  required  to  fill  the 
graduated  portion  is  0.90X2=1.8  grams,  which  is  10  per 
cent  of  18  grams  of  milk.  The  milk  pipette  holds  17.6 
cubic  centimeters,  but  will  deliver  17.5  cubic  centimeters 
of  milk  because  .1  cubic  centimeter  will  adhere  to  the  sides 
of  the  pipette.  The  acid  cylinder  is  graduated  to  deliver 
17.5  cubic  centimeters. 

The  sulphuric  acid  used  for  the  Babcock  test  should  be 


Fig.  69. — Placing  the  milk  in  a  test  bottle. 

of  a  specific  gravity  of  between  1.82  and  1.83  at  60"  Fahren- 
heit. Commercial  acid,  which  is  good  enough  for  this  test, 
is  bought  at  a  density  of  1.84.  To  dilute  this  for  use  in 
the  dairy,  1000  cubic  centimeters  of  the  acid  should  be 
poured  into  45  cubic  centimeters  of  water,  or  100  cubic  centi- 
meters of  water  for  every  ordinary  5-pint  bottle  of  acid. 
In  reducing  the  specific  gravity  of  sulphuric  acid,  always 
pour  the  acid  into  water,  and  never  pour  water  into  the  acid. 


MILK  AND  ITS  PRODUCTS 


207 


After  dilution,  the  acid  must  be  cooled  to  60°  F.  before  being 
used  in  the  test. 

The  details  of  the  test  are  as  follows:  Mix  thoroughly 
the  sample  of  milk,  which  should  be  at  a  temperature  of 
about  60°  F.     Quickly  fill  the  pipette  to  the  mark  with  milk, 


Fig.  70. — Appearance  of  completed  test. 

and  run  the  milk  into  the  test  bottle.  Fill  the  acid  measure 
to  the  mark  with  the  sulphuric  acid  and  pour  the  acid  cau- 
tiously into  the  test  bottle.  Mix  the  milk  and  acid 
thoroughly  by  giving  the  test  bottle  a  rotary  motion.  Let 
the  bottle  and  contents  stand  from  two  to  five  minutes  and 
then  mix  again. 


208  CHEMISTRY  OF  FARM  PRACTICE 

Put  the  test  bottles  in  the  centrifuge  and  whirl  for  four 
or  five  minutes  at  a  speed  of  600-1200  revolutions  per  min- 
ute. Then  add  hot  water  to  fill  the  test  bottle  to  the  neck 
and  whirl  again  for  one  minute;  next  add  hot  water  to  near 
the  top  of  the  graduated  portion  and  whirl  one  minute 
more. 

The  reading  of  the  per  cent  of  fat  should  be  taken  at 
about  130°  F.  This  is  best  accomplished  by  means  of  a 
pair  of  dividers.  The  appearance  of  the  test  bottle  after 
completed  test  is  shown  in  Fig.  70. 

The  results  obtained  in  this  determination  are  due  to  the 
actions  of  strong  sulphuric  acid  and  the  use  of  centrifugal 
force.  The  action  of  the  acid  is  threefold:  It  destroys 
the  adhesive  force  exercised  by  the  casein,  albumin,  sugar, 
and  salts  present  in  the  milk;  the  mixture  of  sulphuric  acid 
and  milk  generates  heat,  which  causes  the  fat  globules  to 
run  together  and  makes  their  separation  from  the  mass 
comparatively  easy;  third,  the  weight  of  the  sulphuric 
acid  increases  the  specific  gravity  of  the  non-fatty  materials, 
causing  the  fighter  fat  the  more  readily  to  rise  to  the  sur- 
face. The  completion  of  the  separation  of  the  fat  is  accom- 
plished by  the  use  of  centrifugal  force  when  the  bottle  con- 
taining the  mixture  is  whirled  in  a  suitable  apparatus,  which 
may  be  run  either  by  hand  or  by  power. 

153.  Determination  of  Specific  Gravity.  The  normal 
specific  gravity  of  milk  from  a  herd  usually  falls  between 
1.030  and  1.034.  The  specific  gravity  of  milk  is  quickly 
determined  by  taking  the  reading  of  a  lactometer  floating  in 
the  milk.  The  lactometer  is  a  specialized  form  of  a  hydrom- 
eter. The  Quevenne  lactometer  has  a  scale  graduated 
from  to  15  to  40°,  corresponding  to  specific  gravities  from 
1.015  to  1.040.  The  milk  should  be  tested  at  a  temperature 
ranging  from  55°  F.  to  60°  F.,  adding  a  correction  of  1° 
(equivalent  to  00.001  specific  gravity)  to  the  reading  for 
each  degree  F.  above  60°  F.  and  subtracting  1°  for  each 
degree  F.  below  60°  F. 


MILK  AND  ITS  PRODUCTS  209 

The  addition  of  water  to  milk  lowers  the  specific  gravity, 
while  the  skimming  of  cream  from  the  milk  raises  the  specific 
gravity.  It  is  therefore  possible,  by  skillful  manipulation, 
for  dishonest  handlers  both  to  water  and  to  skim  the  milk 
so  as  to  leave  it  with  a  specific  gravity  corresponding  to 
normal  milk.  Such  tampering,  however,  will  give  the  milk 
a  suspicious  appearance,  and  if  the  percentage  of  solids, 
not  fat,  falls  below  7.7,  such  milk  may  be  considered  adulter- 
ated. 

154.  Determination  of  Water  and  Total  Solids.  To  de- 
termine the  water  and  total  solids  in  milk  the  procedure  is 
as  follows:  Clean  and  weigh  crystallizing  dishes  with  a 
capacity  of  about  100  cubic  centimeters  or,  if  available,  a 
platinum  dish  3  inches  in  diameter.  Weigh  these  with  small 
glass  rods  in  each  for  use  in  breaking  the  surface  film  so 
as  to  increase  the  rate  of  drying.  With  the  pipette  run  5 
cubic  centimeters  of  the  well-mixed  milk  sample  into  the 
dish  and  obtain  the  exact  weight  of  the  milk.  Dry  it  in  an 
oven  at  100°  C.  or  on  the  surface  of  a  steam  bath  to  constant 
weight.  Two  or  three  hours  ought  to  be  sufficient  for  com- 
plete drying.  Weigh  and  compute  the  dried  residue  as 
total  solid  and  the  loss  by  evaporation  as  water.  If  the 
ash  is  not  to  be  determined,  an  excellent  dish  for  the  deter- 
mination of  water  and  total  solids  is  the  shallow  cover  of 
a  tin  baking-powder  box. 

155.  Determination  of  Ash.  If  a  platinum  or  a  porcelain 
dish  was  used  for  the  determination  of  water  and  total  solids, 
the  dried  residue  from  that  process  may  be  ashed  by  heating 
cautiously  to  a  temperature  just  below  red  heat  till  the  ash 
is  white  or  of  uniform  light  gray  color.  When  the  weight 
is  constant,  compute  the  residue  as  ash. 

156.  Butter.  Butter,  in  addition  to  butter  fat,  con- 
tains water,  curd  and  salt.  In  making  butter,  where  the 
work  is  carefully  conducted,  the  butter  procured  is 
usually  one-sixth  more  than  the  butter  fat  contained  in  the 
cream. 


210 


CHEMISTRY  OF  FARM  PRACTICE 


TABLE    XXIII.— COMPOSITION    OF    CREAMERY  BUTTERS. 

(Wisconsin  Experiment  Station) 


Highest 
Lowest. 
Average 


Per  Cent 

of 

Water. 


17.03 

9.18 

12.77 


Per  Cent 

of 

Fat. 


87.50 

77.07 
83.08 


Per  Cent 

of 

Curd. 


2.45 
0.36 
1.28 


Per  Cent 

of  Salt 
and  Ash. 


4.73 
1.30 

2.87 


Sum  of 

Water,  Curd, 

Salt,  and 

Ash. 


22.95 
12.50 
16.92 


Good  butter  should  contain  at  least  80  per  cent  fat  and, 
preferably,  it  should  run  83  per  cent  fat.  Genuine  butter 
may  usually  be  distinguished  from  oleomargarine  without 
any  special  test.  Most  oleomargarine  is  more  solid  than 
butter  and  is  brittle  and  hard  when  cold.  When  soft,  it  is 
smeary  and  shows  no  grain. 

Process  butter  is  manufactured  from  old  or  poor  butter. 
It  is  first  melted  and  treated  with  steam  to  carry  off  any  of 
the  disagreeable  acids  which  have  resulted  from  the  decom- 
position of  the  fat.  It  is  then  mixed  with  milk,  solidified, 
salted  and  worked.  Process  butter  has  properties  similar 
to  those  of  oleomargarine. 

A  simple  test  for  butter  is  to  heat  it  to  boiling,  carefully, 
in  a  tablespoon.  Good  butter  boils  with  little  noise  and 
spatter  and  produces  an  abundance  of  foam.  Oleomar- 
garine and  process  butter  boil  with  considerable  spattering 
and  produce  little  foam.  The  "  meaty  "  odor  when  hot 
is  characteristic  of  the  animal  fats  used  in  oleomargarine. 

157.  Cheese.  Cheese  is  made  by  coagulating  milk 
when  heated.  American  cheddar-  cheese  is  made  by  heating 
the  milk  to  80°  Fahrenheit  and  adding  a  small  amount  of 
rennet  extract.  The  casein  in  the  milk  is  coagulated  by 
the  rennet  and  holds  the  fat.  The  green  cheese  analyzes 
about  37  per  cent  water,  34  per  cent  fat,  24  per  cent  pro- 
teids,  the  other  5  per  cent  consisting  of  mineral  salts,  lactic 
acid,  and  milk  sugar.  Most  of  the  milk  sugar  and  albumin 
is  drawn  off  in  the  whey. 


MILK  AND  ITS  PRODUCTS  211 

158.  Condensed  Milk.  Condensed  milk  is  manufactured 
either  from  whole  or  partly  skimmed  milk.  In  some  cases, 
sugar  is  added  to  improve  its  keeping  qualities.  Condensed 
milk  should  contain  not  less  than  10  per  cent  fat,  and  must 
be  free  from  preservatives. 


CHAPTER  XX 
INSECTICIDES,  FUNGICIDES  AND  DISINFECTANTS 

159.  Two  Classes  of  Injurious  Insects.  The  insects 
which  are  injurious  to  growing  or  stored  crops  may  be 
separated  into  two  main  classes :  insects  that  bite,  and  those 
that  suck.  Different  remedies  must  be  used  in  combating 
each  class.  Among  the  most  common  biting  insects  are  the 
codling  moth,  potato  bettle,  the  flea  beetle,  the  grass- 
hopper, the  tussock,  brown  tail,  and  gypsy  moths,  the  plum 
curculio,  and  the  various  caterpillars.  The  biting  insects 
are  destroyed  by  spraying  the  plants  eaten  with  some 
poisonous  material  that  will  be  taken  by  the  insect  with  its 
food.  The  materials  commonly  used  for  this  purpose  are 
compounds  of  arsenic  which  has  decided  toxic  effects.  Some 
of  these  substances  are  arsenate  of  lead,  Paris  green,  green 
arsenoid,  London  purple,  and  arsenate  of  lime.  The  last 
named  is  a  product  recently  put  on  the  market. 

Sucking  insects  draw  the  plant  juices  from  the  leaves 
and  the  bark;  the  most  common  are  plant  lice,  the  Chinch 
bug,  San  Jose  scale,  scurfy  scales,  etc.  They  are  killed  by 
materials  that  close  their  breathing  pores,  fill  the  surround- 
ing atmosphere  with  poisonous  fumes,  or  kill  by  reason  of 
their  caustic  properties.  The  following  materials  are  used 
for  this  purpose:  kerosene  emulsion,  soaps,  lime-sulphur 
mixtures,  nicotine  sulphate  solutions,  carbon  bisulphide, 
and  hydrocyanic  acid  gas. 

160.  Injurious  Fungi.  Injurious  fungi  are  minute 
vegetable  organisms  that  attack  living  tissue.  The  fungi- 
cides include  Bordeaux  mixture  (made  from  milk  of  lime  and 
copper  sulphate),  lime-sulphur,  sulphur,  copper  sulphate, 
ammoniacal  copper  carbonate,  and  formaldehyde  solutions. 

212 


INSECTICIDES,  FUNGICIDES  AND  DISINFECTANTS    213 

The  compounds  of  copper  have  decided  poisonous  effects 
upon  the  lower  organisms. 

161.  Insecticides    for    Biting    Insects.       Lead    arsenate 
may  be  purchased  in  the  form  of  a  thick  paste  or  dry  powder. 


Fig.    71. — Pail   spray   for   small    herds.     (Farmers'    Bulletin,    U.  S. 

Dept.  Agr.) 

It  is  prepared  by  the  action  of  lead  nitrate  or  lead  acetate 
on  crystallized  disodium  hydrogen  arsenate.  It  contains 
little  or  no  soluble  arsenic  and,  for  this  reason,  is  especially 
applicable  to  plants  with  tender  foliage.  Lead  arsenate  is 
applied  in  suspension  in  water  or  in  combination  with  fungi- 
cides by  means  of  a  spray,  usually  at  the  rate  2  to  7  pounds 


214  CHEMISTRY  OF  FARM  PRACTICE 

of  the  paste  or  half  of  that  quantity  of  the  powder,  to  50 
gallons  of  the  spray  solution.  Whether  used  as  paste  or 
powder,  the  lead  arsenate  should  first  be  stirred  or  ground 
very  thoroughly  in  a  small  amount  of  the  spray  solution, 
and  gradually  diluted  until  a  very  smooth  paste  is  formed. 

Paris  green  is  a  mixture  of  copper  acetate  and  copper 
arsenite.     It  is  somewhat  more  soluble  than  is  lead  arsenate 


Fig.  72. — Knapsack  sprayer.  The  handle  can  be  removed  and  the 
tank  carried  in  the  hand  instead  of  on  the  back,  if  desired.  (Far- 
mers' Bulletin  243,  U.  S.  Dept.  Agr.) 

and,  for  this  reason,  it  may  injure  tender  foHaged  plants. 
Paris  green  has  been  largely  superseded  as  an  insecticide  by 
lead  arsenate.  It  may  be  applied  dry  by  diluting  with  from 
10  to  50  parts  of  land  plaster,  flour  or  road  dust.  When  used 
in  this  way,  there  is  danger  of  burning  tender  foliage.  A 
solution  of  1  pound  of  Paris  green  and  3  pounds  of  stone 
lime  in  100  to  250  gallons  of  water,  depending  on  the  foliage, 
is  advised. 


INSECTICIDES,  FUNGICIDES  AND  DISINFECTANTS    215 

Green  arsenoid  is  an  insecticide  similar  to  Paris  green,  and 
applied  in  the  same  manner,  but  is  less  used. 

London  purple  is  a  by-product  of  the  manufacture  of 
anilin  dyes.  It  is  composed  of  calcium  arsenate  and  cal- 
cium arsenite  together  with  an  organic  dye  residue.  Lon- 
don purple  is  quite  variable  in  composition,  and  is  very 
little  used. 

162.  Insecticides  for  Sucking  Insects.  Kerosene  emulsion 
is  prepared  by  emulsifying  soap.  A  good  quality  of  laundry 
soap  is  satisfactory.  Two  to  four  pounds  of  soap  and  5  to  10 
gallons  of  kerosene  to  50  to  100  gallons  of  spray  solution  are 
the  usual  proportions.  The  soap  should  be  dissolved  in 
from  5  to  10  gallons  of  hot  water,  placed,  together  with  the 
kerosene,  in  the  spray  barrel,  then  emulsified  by  pumping 
air  through  the  spray  rod  into  the  spray  solution.  Kero- 
sene-emulsion should  be  used  promptly  after  preparation. 

Soaps  are  sometimes  used  to  destroy  soft-bodied  insects. 
Fish-oil  soap  is  one  of  the  best  and  most  commonly  used 
soaps  for  this  purpose.  Potash  soap  is  better  than  soda, 
soap.  The  soap  is  more  easily  dissolved  in  hot  water,  and 
the  solution  applied  by  means  of  the  spray  pump.  A 
solution  of  2  pounds  of  rosin  fish-oil  soap  in  50  gallons  of 
water  is  often  used  as  a  "  sticker  "  for  fungicides  with  poor 
adhesive  qualities. 

Lime-sulphur  mixtures  are  prepared  by  boiUng  sulphur 
with  milk  of  lime.  The  chief  constituents  of  these  mixtures 
are  polysulphides  of  calcium,  the  tetra-  and  the  penta- 
sulphide  being  most  desired,  and  calcium  thiosulphate. 

Nicotine  solutions  are  obtained  from  decoctions  of  tobacco, 
the  nicotine  being  the  active  agent.  One-half  pound  of 
tobacco  is  steeped  in  boiling  water  and  then  diluted  to 
5  or  10  gallons.  These  solutions  are  used  chieflj^  for  the 
control  of  plant  lice. 

Nicotine  sulphate  solutions,  such  as  Black  Leaf — 40  are 
used  extensively  and  have  replaced  kerosene  emulsion  for 
aphis. 


216  CHEMISTRY  OF  FARM  PRACTICE 

Carbon  bisulphide  (CS2)  when  partially  decomposed  by 
standing  is  a  vile-smelling  liquid  which  vaporizes  at  ordinary 
temperatures.  Its  use  in  the  field  is  limited,  being  mainly 
confined  to  the  control  of  certain  root-infesting  plant  lice. 
It  is  extensively  used  for  the  control  of  insects  in  granaries. 
In  tight  cribs  it  is  best  appUed  on  top  of  grain  or  corn  at 
the  rate  of  6  pounds  to  100  bushels  applied  when  the  tem- 
perature is  above  65°  F. 

Hydrocyanic  acid  gas  (HCN)  is  prepared  by  treating 
potassium  cyanide  with  excess  of  sulphuric  acid;  2KCN 
+112804  =  2HCN+K2SO4.  This  gas  is  very  poisonous 
and  its  use  is  not  advised.  When  used,  the  proportion  of 
1  pound  of  the  potassium  cyanide,  2  pounds  of  sulphuric  acid 
and  4  pounds  of  water  gives  a  rapid  evolution  of  the  gas. 
Care  must  be  exercised  n^t  to  inhale  the  extremely  poisonous 
fumes. 

163.  Fungicides.  Bordeaux  mixture  is  prepared  from 
copper  sulphate  (CUSO4)  and  calcium  hydrate  (Ca(0H)2). 
The  most  common  proportions  are  4  pounds  of  copper  sul- 
phate and  4  pounds  of  quicklime  to  50  gallons  of  water. 
The  copper  sulphate  should  be  dissolved  and  made  up  to 
25  gallons  of  water.  The  lime  should  be  carefully  slaked 
with  water  and  made  to  twenty-five  gallons.  Pour  the 
dilute  solutions  into  the  spray  barrel,  stirring  vigorously 
and  use  while  fresh.  The  above  proportions  may  be  widely 
varied  to  meet  special  needs. 

Copper  sulphate  is  difficult  to  dissolve.  The  solution 
may  best  be  accomplished  by  putting  the  powdered  crystals 
in  a  small  bag  which  is  suspended  over  night  in  the  water, 
near  the  surface.  The  copper  sulphate  solution,  being  more 
dense  than  water,  sinks,  leaving  the  copper  sulphate  crystals 
in  constant  contact  with  an  unsaturated  solution.  Powdered 
portions  of  the  crystals  will  dissolve  rapidly  in  hot  water. 

Lime-sulphur  has  already  been  discussed.  As  a  fungicide 
for  plants  in  foliage,  the  commercial  product,  32°  Baume,  is 
applied  at  the  rate  of  1  to  2  gallons  in  50  gallons  of  water. 


INSECTICIDES,  FUNGICIDES  AND  DISINFECTANTS    217 

depending  upon  the  liability  of  the  plant  to  lime-sulphur 
injury. 

Self-boiled  lime-sulphur  is  prepared  from  quick-lime  (CaO) 
and  sulphur  flour.  The  sulphur  is  put  in  suspension  through 
the  agency  of  the  slaking  lime,  very  little  chemical  union  of 
lime  and  sulphur  probably  occurring.     The  usual  proportions 


Fig.  73. — Barrel  spray  pump  with  hose  and  bamboo  extension  rods 
for  orchard  spraying.     (Farmers'  Bulletin  243,  U.  S.  Dept.  Agr.) 


are  8  pounds  of  lime  and  8  pounds  of  sulphur  in  50  gallons 
of  water.  The  process  is  carried  out  to  best  advantage 
when  four  times  the  above  quantities  are  used.  This  spray 
is  especially  adapted  to  use  on  tender-foliaged  plants. 

Finely  divided  sulphur  in  suspension  is  largely  replacing 
self-boiled  lime-sulphur  and  ordinary  lime-sulphur.  Several 
proprietary  preparations  of  this  nature  are  on  the  market. 


218 


CHEMISTRY  OF  FARM  PRACTICE 


They  are  more  expensive  than  self-boiled  lime-sulphur,  and 
about  equally  effective.  Their  advantages  are  that  they  are 
more  easily  prepared  and  that  they  leave  less  residue  upon 
both  fruit  and  foliage. 


Fig.  74. — Gasoline  power  spray.     (Bulletin  243,  U.  S.  Dept.  Agr.) 


Copper  sulphate  (CUSO4)  is  used  as  a  dormant  spray  for 
certain  types  of  fungus  diseases  of  plants.  A  notable 
example  of  this  is  its  use  in  connection  with  the  control  of 
peach  leaf  curl.     It  is  one  of  the  most  toxic  of  fungicides, 


INSECTICIDES,  FUNGICIDES  AND  DISINFECTANTS    219 

but  its  period  of  activit}'  is  of  short  duration,  due  to  the 
fact  that  it  is  quickly  washed  off  the  plant.  Copper  sulphate 
is  very  successfully  used  for  the  destruction  of  algae  in  water. 

Ammoniacal  copper  carbonate  (Cu(NH3)4C03)  is  used 
in  special  cases  on  ornamental  plants  and  on  certain  fruits 
just  before  ripening,  where  residues  from  other  sprays 
would  be  objectionable.  The  chief  objections  to  this  prep- 
aration are  its  relatively  high  toxicity  to  the  host  plant, 
its  cost,  and  the  difficulty  of  its  preparation. 

Formaldehyde  solutio7is  (CH2O)  are  chiefly  used  for  the 
treatment  of  seeds  and  vegetable  reproductive  materials, 
as  tubers,  to  rid  them  of  disease  l)efore  planting.  The 
solution  is  prepared  by  adding  1  pint  of  formalin  to  30  gal- 
lons of  water. 

164.  Common  Disinfectants.  Disinfectants  are  used  to 
destroy  organisms  that  bring  on  di8ec4,se,  decay,  and  dis- 
agreeable odors.  There  are  several  common  and  effective 
kinds.  In  handling  disinfectants  great  care  should  be  exer- 
cised, as  many  are  very  poisonous. 

Lime.  Unslaked  lime  (CaO)  and  water-slaked  lime 
(Ca(0H)2)  are  the  cheapest  and  most  easily  obtained  dis- 
infectants. Air-slaked  lime  (CaCOs)  has  no  disinfecting 
properties  except  that  due  to  absorption.  Lime  that  is  to 
be  used  for  disinfecting  purposes  should  be  kept  in  recep- 
tacles that  are  tight  enough  to  exclude  air.  It  is  best  applied 
in  the  form  of  milk  of  lime,  prepared  as  follows:  Treat 
a  lump  of  quick-lime  in  a  covered  vessel  with  water  until 
a  creamy  liquid  is  formed.  This  should  be  kept  in  an  air- 
tight receptacle  when  not  in  use.  Quicklime  may  be  pul- 
verized and  sprinkled  on  dry;  this  form  is  especially  useful 
in  closets,  replacing  earth. 

Chlorinated  Lime  (Bleaching  powder,  CaCl20),  This 
material  is  prepared  by  showering  slaked  lime  powder 
through  chlorine  gas.  It  is  a  white  powder,  which  decom- 
poses slowly  on  exposure  to  moisture,  giving  off  hypochlorous 
acid,  which  is  the  substance  that  gives  the  characteristic 


220  CHEMISTRY  OF  FARIM  PRACTICE 

odor  to  bleaching  powder.  It  should  be  kept  in  sealed  con- 
tainers. Chlorinated  lime  is  prepared  for  use  by  mixing  in 
the  proportion  of  6  ounces  of  the  powder  to  each  gallon  of 
water.  It  is  largely  used  for  the  disinfection  of  refuse, 
stock-pens,  or  cars,  and  is  the  most  efficient  disinfectant. 
It  has  a  bleaching  effect  on  fabrics  when  there  is  need  of 
concentrated  effect;  the  chlorinated  lime  may  be  treated 
with  dilute  acid. 

Formaldehyde.  Formaldehyde  (HCHO)  is  commonly 
purchased  under  the  name  formalin,  which  is  a  solution  con- 
taining about  40  per  cent  formaldehyde.  It  may  be  used 
for  disinfecting  purposes  either  as  a  liquid  or  as  a  gas.  A 
5  per  cent  solution  of  formalin  is  considered  to  be  superior 
to  carbolic  acid  of  the  same  strength,  as  a  disinfectant. 
Formaldehyde  is  peculiarly  effective  as  a  disinfectant,  as  it  is 
an  unstable  compound  which  on  the  one  hand  is  easily  re- 
duced to  methyl  alcohol  by  the  addition  of  hydrogen  or  of 
reducing  agents,  which  it  abstracts  from  the  organism  which 
needs  disinfection,  and  on  the  other  hand,  it  is  easily  oxidized 
into  formic  acid  by  the  addition  of  oxygen,  which  it  takes  from 
the  substance  to  be  disinfected — in  either  case  sterilizing  the 
infecting  material. 

These  opposing  actions  are  represented  by  the  following 
equations: 

HCHO+PIo     =     CH:jOH 

Formal(l(!hy<le  Methyl  alcohol 

HCHO+0       =     HCOOH 

Formaldehyde  Formic  acid 

When  disinfecting  with  gaseous  formaldehyde,  it  is  neces- 
sary to  close  tightly  the  place  to  be  disinfected  in  order  that 
the  concentrated  gas  may  be  in  contact  with  the  infected 
material  for  some  time  and  the  temperature  should  be  warm. 
The  gas  may  be  produced  from  formalin  in  several  ways, 
but  the  chemical  means  are  usually  most  convenient.  The 
various  methods  are:  heating  under  pressure,  heating  with- 


INSECTICIDES,  FUNGICIDES  AND  DISINFECTANTS     221 

out  pressure,  spraying  and  by  an  oxidizing  agent.  The 
last  two  are  ordinarily  used.  When  spraying  is  resorted  to, 
the  compartment  should  be  kept  closed  for  at  least  twenty- 
four  hours.  An  ounce  of  formalin  is  required  to  each 
100  cubic  feet,  therefore  a  room  10  feet  square  and  10  feet 
high  would  require  ten  ounces.  The  formalin  is  sprayed 
on  sheets  hung  in  the  room. 

The  gas  is  readily  lil)erated  by  several  chemicals,  but  the 
use  of  potassium  permanganate  has  found  most  favor.     The 


Fig.  75. — Making  Bordeaux  mixture.  The  two  men  pour  together 
the  diluted  Hme  milk  and  the  bluestone  solution  into  a  barrel  or 
spray  tank  and  stir  well.     (Bulletin  243,  U.  S.  Dept.  Agr.) 


proportion  which  is  most  effective  seems  to  be  6  parts  of 
formaUn  to  5  parts  of  potassium  permanganate.  For  dis- 
infecting 1000  feet  of  space,  20  ounces  of  formalin  and  161 
ounces  of  potassium  permanganate  are  required.  The  crystals 
of  potassium  permanganate  may  be  placed  on  the  bottom 
of  an  ordinary  dishpan  and  the  formalin  poured  on  quickly 
in  order  that  the  person  so  engaged  may  make  a  rapid  exit. 
Some  of  the  formaldehyde  is  oxidized  to  formic  acid  by  the 
permanganate  and  this  generates  heat  enough  to  drive  the 
remainder  out  as  a  gas.     The  compartment  should  be  kept 


222  CHEMISTRY  OF  FARM  PRACTICE 

closed  for  not  less  than  twelve  hours.  The  temperature  of 
the  room  should  not  be  less  than  65°  F.  for  the  treatment 
to  be  effective.  It  is  well  to  sprinkle  the  floor  and  other 
objects  not  harmfully  affected  by  water,  before  the  treat- 
ment, as  it  is  more  effective  in  a  damp  atmosphere. 

Sulphur.  Barns  and  other  outbuildings  may  be  more 
cheaply  but  not  as  thoroughly  disinfected  with  sulphur 
fumes.  These  fumes  bleach  fabrics  and  discolor  some  paints, 
for  which  reason  their  use  is  not  always  to  be  recommended. 
Use  not  less  than  4  pounds  of  sulphur  to  each  1000  cubic  feet. 
Break  the  roll  sulphur  into  small  pieces  and  put  them  into 
an  iron  pot  which  should  be  set  in  a  tub  containing  a  few 
inches  of  water  as  a  preventive  of  fire.  Pour  alcohol  on  the 
sulphur  and  ignite.  If  possible,  keep  the  compartment  closed 
for  twelve  hours. 

Carbolic  Acid.  Carbolic  acid  or  phenol  (CeHsOH)  has 
been  extensively  used  as  a  disinfectant  for  years.  It  is 
poisonous  and  should  be  carefully  handled.  Pure  carbolic 
acid  is  a  solid  at  ordinary  temperatures  and  crystallizes  into 
long  pink  or  white  needles.  It  is  often  sold  in  the  liquid 
form,  which  is  prepared  by  adding  1  part  of  water  to  9 
parts  of  the  crystals.  Carbolic  acid  used  in  the  proportion 
of  1  part  of  acid  to  20  parts  of  water  is  a  very  effective 
disinfectant.  The  carbolic  acid  is  not  readily  soluble: 
for  this  reason  it  should  be  carefully  dissolved  in  warm  water. 
When  garments  are  to  be  disinfected  they  should  remain  in 
the  solution  prepared  as  directed  above  for  not  less  than 
one  hour. 

Carbolic  acid  is  poisonous,  expensive  and  will  destroj^ 
the  spores  of  anthrax  and  other  spore-forming  bacteria.  It 
has  several  advantages  in  that  it  destroys  non-spore-bearing 
bacteria,  is  little  interfered  with  by  albuminous  matter, 
when  diluted  does  not  destroy  fabrics  nor  corrode  metals, 
and  that  it  is  easily  obtained  at  any  drug  store. 

Crude  Carbolic  Acid.  Crude  carbolic  acid  is  very  exten- 
sively used  as  a  disinfectant.     It  is  variable  in  its  composi- 


INSECTICIDES,  FUNGICIDES  AND  DISINFECTANTS    223 

tion  and  uncertain  in  its  effects.  It  consists  of  a  mixture  of 
coal  tar  oils,  cresol  and  a  very  little  phenol.  The  oil  has 
practically  no  disinfectant  properties,  although  the  odor  is 
popularly  considered  an  indication  that  disinfection  is  being 
accomplished.  Its  value  as  a  disinfectant  depends  on  the 
content  of  cresol.  When  the  cresol  content  is  known,  the 
material  should  be  diluted  until  it  contains  2  per  cent  of 
that  acid. 

Cresol  (CH3C6II4OII),  tricresol,  straw-colored  carbolic 
acid,  or  liquid  carbolic  acid  as  it  is  variously  termed,  is  found 
on  the  market  in  various  degrees  of  purity.  Cresol  as  de- 
scribed by  the  United  States  Pharmacopoeia  is  a  colorless 
liquid  having  an  odor  similar  to  carbolic  acid.  On  account 
of  a  small  amount  of  impurities  it  is  usually  sold  of  a  90  to 
98  per  cent  purity.  It  should  not  contain  less  than  90  per 
cent  cresylic  acid,  as  the  cresol  containing  less  amounts  usually 
carries  enough  coal  tar  oil  to  interfere  with  the  solution  of 
the  cresol  in  water.  This  material  is  relatively  cheap  and 
well  suited  to  disinfect  yards,  barns,  and  cars.  The  solu- 
tion used  for  disinfecting  should  contain  about  2  per  cent  of 
cresol,  which  is  said  to  be  more  effective  than  5  per  cent 
carbolic  acid.  It  is  applied  the  same  as  the  carboUc  acid 
solution.  This  material  is  not  readily  soluble  in  water, 
hence  care  must  be  exercised  to  get  a  strong  enough  solution. 
Its  advantages  are  that  it  is  cheap,  does  not  destroy  fabrics 
or  metals,  is  more  effective  than  carbolic  acid  for  destroying 
spore-forming  bacteria,  and  its  action  is  not  hindered  by 
albuminous  substances. 

Cresol  is  made  more  soluble  by  mixing  with  an  equal  part 
of  linseed-oil-potash  soap.  Care  must  be  taken  to  assure  the 
presence  of  50  per  cent  of  actual  cresol  in  the  mixture. 
There  should  be  3  or  4  per  cent  of  cresol  in  this  sort  of  a 
mixture  when  used  for  disinfecting,  hence  an  increase  in  cost 
over  the  straight  cresol  solution. 

Bichloride  of  Mercury.  Bichloride  of  mercury  (HgCl2) 
is  a  white  crystalline,  poisonous  substance.     It  is  prepared 


224  CHEMISTRY  OF  FARM  PRACTICE 

in  tablet  form  mixed  with  ammonium  chloride  (NH4CI), 
which  facilitates  its  solubility.  It  is  used  in  the  proportions 
of  1  to  500  or  1  to  1000.  It  combines  with  albuminous  sub- 
stances and  is  rendered  inert.  This  material  is  a  powerful 
germicide,  but  it  is  a  deadly  poison. 

All  disinfectants  are  selected  because  of  their  chemical 
activity,  and  care  should  be  exercised  in  handling  them 
because  of  their  poisonous  nature.  The  remnants  after  use 
should  be  destroyed  rather  than  stored. 


CHAPTER  XXI 

PAINTS  AND  WHITEWASHES 

165.  Paints.  Few  farmers  realize  fully  the  economic 
value  of  paint  on  farm  buildings  and  farm  machines;  its 
use  is  sometimes  regarded  as  a  luxury  that  may  readily  be 
dispensed  with.  Paint  not  only  improves  the  appearance  of 
the  various  objects  to  which  it  is  applied,  but  it  has  a  greater 
value  in  preventing  or  delaying  the  rusting  or  decaying  of 
both  machinery  and  buildings,  thereby  increasing  their 
length  of  service.  One  does  not  have  to  be  a  skilled  painter 
to  do  the  ordinary  painting  on  the  farm.  With  the  aid  of 
a  few  inexpensive  utensils,  paint  may  readily  be  apphed. 

Paint  consists  of  a  pigment  or  of  several  pigments  held 
in  suspension  by  a  liquid,  or  vehicle,  as  it  is  called.  If  the 
paint  is  to  be  used  for  outside  work  it  must  be  insoluble  in 
water  and  possess  a  high  resistance  to  the  chemical  action  of 
atmospheric  elements.  Pigments  are  stable  organic  bodies 
or  mineral  compounds  which  are  used  to  impart  either  a 
protective  covering  or  a  color  or  both,  by  mechanical  ad- 
hesion or  by  admixture  with  the  substance  to  be  painted. 
The  color  of  a  pigment  is  dependent  upon  the  amount  and 
kind  of  Ught  that  it  reflects.  It  should  be  opaque  if  it  is 
desired  to  conceal  the  surface  to  which  it  is  applied.  The 
vehicle  is  the  liquid  portion  of  the  paint  and  is  usually 
a  drying  oil;  sometimes  water  with  gum  or  size  is  used 
for  inside  work.  Linseed  oil  seems  to  be  the  best  oaint 
vehicle. 

166.  Drying  Oils.  The  so-called  drying  oils  are  named 
for  their  peculiar  property  of  hardening.  When  linseed 
oil,  and  any  one  of  a  number  of  other  oils  having  somewhat 
similar  properties,  is  spread  in  a  thin  layer  over  a  surface, 

225 


226  CHEMISTRY  OF  FARM  PRACTICE 

it  will  dry  and  set  in  a  hard  film,  due  to  the  absorption  of 
oxygen  from  the  atmosphere.  Corn  oil  and  soybean  oil, 
to  a  limited  extent,  behave  in  a  similar  manner.  The  dry- 
ing of  these  oils  is  aided  by  sunlight  and  hindered  by  mois- 
ture; it  does  not  occur  in  the  absence  of  oxygen.  Boiled 
oil  dries  more  quickly  than  raw  oil. 

167.  Driers.  The  drying  of  paints  may  be  hastened  by 
certain  compounds  of  lead  and  manganese  which  are  known 
as  driers.  When  the  drier  is  applied  in  the  form  of  a  liquid 
it  is  known  as  a  Japan  drier.  The  use  of  a  small  amount 
of  a  drier  seems  more  effective  than  when  a  large  amount  is 
applied.  With  an  excessive  amount  of  drier  the  film  pro- 
duced is  not  so  durable.  Some  pigments,  red  lead  for 
example,  act  as  driers  as  well  as  pigments.  It  is  generally 
believed  that  the  greater  the  proportion  of  the  pigment  the 
more  resistance  the  film  will  show,  provided  that  all  of  the 
particles  of  the  pigment  are  covered  with  oil. 

For  thinning  paint  to  make  it  work  easier,  certain  vola- 
tile materials  are  used,  such  as  turpentine  or  benzine. 

168.  White  Pigments.  White  lead  is  the  most  important 
of  all  pigments.  This  material  is  a  basic  lead  carbonate  in 
which  there  are  two  molecules  of  lead  carbonate  to  one  mole- 
cule of  lead  hydroxide  (2PbC03-Pb(OH)2).  White  lead 
is  very  heavy,  being  6.47  tirnes  heavier  than  the  same  volume 
of  water.  Its  great  value  as  a  pigment  is  due  to  its  covering 
power,  its  permanency,  and  to  the  readiness  with  which  it 
mixes  with  other  pigments.  Like  all  lead  compounds  it  is 
poisonous. 

Sublimed  White  Lead.  This  has  recently  come  into  ex- 
tensive use.  It  has  good  covering  power  and  color,  mixes 
well  with  pigments  containing  sulphur,  and  is  more  durable 
in  sea  air  than  is  white  lead.  With  linseed  oil  it  dries  rapidly, 
forming  a  tough,  impervious  coating.  Sulphur  fumes  will 
not  affect  it  quickly.  For  these  reasons  it  is  frequently 
used  as  a  substitute  for  white  lead.  It  is  composed  of  75 
per  cent  lead  sulphate,  20  per  cent  lead  oxide  and  5  per  cent 


PAINTS  AND  WHITEWASHES  227 

zinc  oxide.  Whether  it  is  a  mixture  or  a  compound  is  not 
determined. 

Zinc  Oxide  or  Chinese  White.  This  material  works  well 
in  oil,  requiring  a  very  large  amount,  approximately  20  per 
cent  of  its  weight,  and  is  used  as  a  house  paint  and  as 
an  enamel  for  inside  surfaces  as  bathtubs,  plumbing,  etc. 
It  is  the  whitest  of  all  the  paint  pigments.  It  will  not 
collect  dust  as  much  as  does  white  lead.  When  mixed  with 
white  lead  it  retards  or  entirely  prevents  the  discoloration 
of  the  latter  by  hydrogen  sulphide. 

Lithopone.  Thisis  a  mixture  of  zinc  sulphide  and  barium 
sulphate,  hea',^d,  suddenly  chilled  and  then  ground.  This 
material  has  a  brilliant  color,  and  more  body  than  has  white 
zinc.  It  is  permanent,  is  fine  in  texture  and  mixes  well 
with  oil  and  other  pigments,  except  those  containing  lead  or 
copper.  It  is  used  advantageously  as  a  marine  paint.  It  is 
largely  used  in  the  oilcloth  industry. 

Barytes.  Barium  sulphate  is  very  heavy,  and  may  be 
mixed  with  all  pigments,  but  it  has  little  body,  dries  slowly, 
and  does  not  mix  well  with  oil.  When  used  as  an  adulterant 
of  white  lead  its  use  is  to  be  avoided.  When  applied  in 
limited  amount  as  an  extender  in  mixed  paint,  it  imparts 
desirable  qualities.  It  is  used  by  the  United  States  Navy 
as  a  basis  for  battle-ship  gray. 

169.  Green  Pigments.  Brunswick  green  is  oxychloride 
of  copper.  This  pigment  works  well  with  oil,  has  a  fair 
covering  power,  but  is  rather  pale  in  color.  Other  pigments 
sold  under  this  name  consist  of  a  mixture  of  Prussian  blue, 
chrome  yellow,  and  barytes  in  varying  proportions.  They 
work  well  in  oil,  have  good  covering  power,  and  last  fairly 
well,  but  they  cannot  be  used  with  alkaline  substances,  com- 
pounds of  sulphur,  or  in  the  presence  of  hydrogen  sulphide. 

Chrome  greens  are  mixtures  of  chrome  yellow  and  Prussian 
blue.  They  are  yellowish  green  in  color,  mix  well  with  oil 
and  with  other  colors,  have  good  covering  power,  and  are 
permanent. 


228  CHEMISTRY  OF  FARM  PRACTICE 

170.  Blue  Pigments.  Ultramarine  blue  is  probably  a 
double  silicate  of  sodium  and  aluminum  and  sulphide  of 
sodium.  The  composition  is,  however,  somewhat  variable. 
It  is  the  most  important  blue  pigment.  Ultramarine  is 
very  sensitive  to  acids.  In  addition  to  its  use  as  a  pig- 
ment in  paints  it  is  used  in  coloring  wall-paper,  in  calico 
printing  and  for  neutralizing  yellow-colored  sugar,  paper 
pulp,  and  cloth.  It  may  also  be  made  by  grinding  up  the 
mineral  lapis  lazuli.  This  is  not  so  easily  affected  by  acids 
but  has  not  so  brilliant  a  color. 

Prussian  blue  is  ferrocyanide  of  iron.  It  is  not  affected 
by  acids,  mixes  well  with  oil,  but  the  color  is  destroyed  by 
alkalies.  It  has  good  coloring  powers,  but  is  transparent 
and  lacks  body. 

171.  Red  Pigments.  Red  lead  is  lead  tetroxide  (Pb304). 
It  is  a  pigment  of  great  brilliancy  when  a  good  compound 
is  secured  and  it  has  remarkable  covering  power.  It  is 
made  by  heating  litharge  (PbO). 

Iron  reds  are  prepared  in  large  quantities  as  by-products 
from  other  manufactures.  They  are  valuable  pigments, 
being  very  permanent.  These  pigments  are  not  very  bright, 
but  they  have  several  advantages;  they  work  well  in  oil, 
mix  with  other  pigments,  have  good  body  and  are  cheap. 
They  are  compounds  of  ferric  oxide  (Fe203). 

Vermilion  is  mercuric  sulphide  (HgS).  It  is  a  heavy, 
opaque,  brilliant  pigment  which  does  not  work  well  with 
oil  on  account  of  its  weight.  It  is  quite  permanent,  and 
readily  affected  by  either  acids  or  alkalies,  but  it  is  very 
expensive. 

172.  Yellow  Pigments.  Chrome  yellows  are  chromate 
of  lead,  zinc,  or  barium,  each  having  a  characteristic  shade. 

Lead  chromate  is  a  brilliant  yellow  which  mixes  well  with 
oil  and  has  great  covering  powers.  If  treated  with  a  caustic 
alkali,  its  color  changes  to  orange  or  red. 

Yellow  ochres  are  natural  mineral  products  which  vary  in 
color,  the  color  being  due  to  hydrated  oxide  of  iron. 


PAINTS  AND  WHITEWASHES  229 

173.  Brown  Pigments.  Umbers  are  ochres  containing 
a  large  amount  of  manganese.  The  best  umber  comes 
from  Cyprus;  it  is  very  permanent,  has  good  covering 
power,  and  mixes  well  with  other  pigments.  It  is  neither 
affected  by  acids  nor  alkalies  and  it  is  very  cheap. 

Vandyke  browns  are  mixtures  of  iron  oxides  and  organic 
matter.  They  are  permanent,  mix  well  with  other  pig- 
ments, and  have  good  body. 

174.  Black  Pigments.  Lampblack,  as  well  as  the  other 
black  pigments,  has  carbon  for  its  basis.  Lampblack  is 
permanent,  of  good  covering  power,  and  fine  grained.  It  is 
difficult  to  mix  with  water  or  oil  and  dries  slowly. 

175.  Mixing  Paints.  The  main  object  in  mixing  paint 
is  to  get  every  particle  of  the  pigments  in  contact  with  the 
vehicle.  The  pigments  are  purchased  dry  or  in  the  paste 
form  mixed  with  a  small  amount  of  the  vehicle.  The 
latter  form  is  usually  preferable,  because  the  pigment  has 
been  ground  in  a  small  amount  of  the  vehicle  in  preparation 
and  its  dilution  is  easier  than  the  suspension  of  the  dry 
pigment. 

A  small  hand  mill  can  be  purchased  for  about  SIO  that 
is  satisfactory  for  mixing  paints.  For  small  jobs  the  ready 
mixed  paints  are  more  economical. 

176.  Whitewashes.  Government  whitewash  is  prepared 
by  slaking  one-half  bushel  of  good  quicklime  in  hot  water, 
keeping  it  covered  while  slaking.  Strain  and  add  4  quarts 
of  salt,  dissolved  in  warm  water,  3  pounds  of  ground  rice 
boiled  to  a  thin  paste,  |  pound  Spanish  whiting,  and  1  pound 
of  clear  glue,  dissolved  in  warm  water.  Mix  and  let  stand 
for  several  days.  Keep  the  wash  thus  prepared  in  a  kettle 
or  portable  furnace,  and  when  used  put  it  on  as  hot  as  possi- 
ble with  a  painter's  brush  or  a  whitewash  brush.  This 
wash  may  be  made  in  quantities  and  heated  as  needed,  but 
it  should  be  put  on  hot. 

Factory  whitewash  is  used  for  interior  work.  Slake  1 
bushel  (62  pounds)  of  quicklime  with  15  gallons  of  water; 


230  CHEMISTRY  OF  FARM  PRACTICE 

keep  the  barrel  covered  and  stir  occasionally.  Beat  up 
separately  2^  pounds  of  rye  flour  in  |  gallon  of  cold  water, 
then  add  2  gallons  of  boiling  water.  Then  dissolve  2^ 
pounds  of  rock  salt  in  2|  gallons  of  hot  water.  Pour  the 
last  two  preparations  into  the  first. 

Waterproof  Whitewash.  Slake  1  bushel  of  quicklime 
with  12  gallons  of  hot  water.  Then  dissolve  separately 
2  pounds  of  common  table  salt  and  1  pound  of  zinc  sulphate 
in  2  gallons  of  boiling  water.  Pour  the  last  preparation  into 
the  first  and  add  2  gallons  of  skimmed  milk. 

177.  Special  Ingredients  for  Whitewash.  An  ounce  of 
alum  added  to  each  gallon  of  lime  whitewash  increases  its 
sticking  properties.  A  pint  of  molasses  to  5  gallons  of  white- 
wash renders  the  Ume  more  soluble  and  increases  its  pene- 
tration. Sihcate  of  soda  solutions  aid  in  fireproofing, 
while  1  pound  of  bar  soap  dissolved  and  added  to  5  gal- 
lons of  whitewash  gives  it  a  gloss. 

178.  Calcimine.  The  basis  of  calcimine  is  whiting,  or 
carbonate  of  Hme.  This  material  is  carried  in  water  as  a 
vehicle  and  is  made  to  adhere  by  the  use  of  glue.  Damp- 
proof  calcimine  is  prepared  by  thoroughly  mixing  16  pounds 
of  Paris  white  or  extra  gilders'  whiting  with  1  gallon  of  boil- 
ing water.  Soak  separately  |  pound  of  white  sizing  glue 
for  four  horn's  in  ^  gallon  of  cold  water,  then  dissolve  by 
heating  on  a  water  bath.  Also,  dissolve  4  ounces  of  sodium 
phosphate  in  1  pint  of  boihng  water.  Mix  the  last  with  the 
first  and  add  the  second.  For  tinting  use  yellow  ochres, 
sienna,  mnbers,  Venetian  red,  para-red,  maroon,  oxid, 
ultramarine  blue,  ultramarine  green,  chromium  oxide,  or 
bone  black,  none  of  which  is  affected  by  hme. 

If  lampblack  is  used  for  tinting,  it  must  be  stirred  in  hot 
water  containing  a  httle  soap  or  in  cold  water  containing 
a  little  borax,  the  alkah  serving  to  overcome  the  greasy 
nature  of  the  lampblack. 

179.  Varnishes.  A  varnish  is  a  dissolved  resin,  or  a 
drying  oil,  which,  when  exposed  to  the  air,  becomes  hard 


PAINTS  AND  WHITEWASHES  231 

and  impervious  to  air  and  water.  After  the  varnish  is 
applied,  the  solvent  evaporates,  leaving  the  resin,  or  the  oil 
oxidizes  and  dries. 

Spirit  varnish  consists  of  resin  dissolved  in  alcohol, 
petroleum  spirits  or  some  other  volatile  solvent.  Turpentine 
varnishes  are  those  in  which  turpentine  is  the  solvent  used. 
Linseed  oil  varnishes  may  consist  of  linseed  oil  alone,  or 
resin  and  turpentine  may  be  added.  The  addition  of  tur- 
pentine tends  to  overcome  the  tendency  to  scale  off.  The 
most  important  varnishes  are  made  with  shellac,  while 
mastic,  sandarac,  and  dammar  are  som*etimes  used. 

Oil  Varnish.  The  greater  part  of  the  varnishes  made  are 
compounded  of  hnseed  oil,  resin  and  turpentine.  Tur- 
pentine varnishes  dry  slowly  but  they  are  tough  and  flexible. 
Linseed  varnishes  are  the  most  important,  but  they  do  not 
show  the  surface  brilliancy  that  some  other  varnishes  show. 

180.  Shellac.  Shellac  is  a  form  of  the  resin  lac  which  is 
produced  by  the  bite  of  certain  insects  on  the  small  twigs 
of  several  species  of  trees  which  grow  in  the  East  Indies. 
The  insects  feed  on  the  plant  sap  and  exude  the  lac,  which 
finally  covers  the  insect  and  her  eggs.  The  twigs  bearing 
these  exudations  are  collected  and  appear  commercially  as 
stick  lac.  The  crude  material  is  first  treated  by  macerating 
in  warm  water  to  remove  a  red  dye-stuff  that  it  carries.  This 
material  is  sold  as  lac-dye,  and  the  residue  from  the  macera- 
tion is  known  as  seed-lac.  This  is  refined  by  melting  and 
straining  through  muslin  bags.  The  melted  lac  is  poured 
in  thin  films  over  cold  surfaces,  to  which  it  will  not  adhere, 
and  is  allowed  to  cool.  These  flakes  are  sold  as  shellac. 
Shellac  is  completely  soluble  in  caustic  alkalies  and  in  borax 
solutions.  It  is  partly  soluble  in  alcohol,  turpentine,  chloro- 
form or  ether. 

181.  Glue.  Glue  is  a  product  of  the  decomposition  of 
animal  connective  and  elastic  tissues.  It  contains  two  essen- 
tial constituents,  gluten  and  chondrin.  The  former  has 
great  adhesive  properties  and  the  latter  is  adhesive  to  a  less 


232  CHEMISTRY  OF  FARM  PRACTICE 

extent.  Glues  are  variously  termed  hide  glue,  hone  glue 
and  fish  glue,  due  to  the  source  from  which  they  are  derived. 
Bone  glue  and  hide  glue  have  essentially  the  same  general 
characteristics,  while  fish  glue  has  less  jellying  properties. 
Liquid  glue  is  made  by  treating  fish  glue  with  acetic,  hydro- 
chloric, or  nitric  acid,  any  one  of  which  will  cause  the  loss  of 
the  property  of  gelatinizing  when  cold. 


CHAPTER  XXII 

MATERIALS  PRODUCING  HEAT  AND  LIGHT— FIRE 
EXTINGUISHERS 

182.  Petroleum.  Crude  petroleum  is  found  in  enormous 
quantities  in  oil-bearing  rock  strata.  The  world's  production 
of  this  most  important  material  in  the  year  1912  was 
350,000,000  barrels.  California,  Oklahoma,  Illinois,  West 
Virginia,  Texas,  Louisiana,  Ohio  and  Pennsylvania  are  the 
principal  sources  of  supply  in  this  country,  which  furnishes 
62  per  cent  of  the  world's  production.  In  other  countries 
Russia  is  the  largest  producer  (19  per  cent) .  Petroleum  from 
the  Appalachian  fields  is  a  thick  greenish  liquid.  It  is 
composed  of  a  mixture  of  many  hydrocarbons,  some  of  which 
contain  sulphur.  Petroleum  is  economically  conveyed 
through  pipe  lines,  one  of  these  extending  from  the  Okla- 
homa field  via  Kansas  City  and  Chicago  to  the  seaboard, 
a  distance  of  1600  miles. 

Petroleum  is  the  source  of  very  many  substances  of  great 
value,  as  for  the  production  of  illumination,  for  fuel  and  for 
lubrication.  By  processes  of  distillation  at  different  tem- 
peratures these  products  are  separated  from  the  petroleum 
and,  passing  off  as  vapors,  are  turned  into  liquids  by  conden- 
sation. In  the  distillation  the  products  of  low-boiling 
points  coming  off  first  are  in  succession  petroleum-ether, 
gasoline,  naphtha,  benzine  and  kerosene.  The  remaining 
oil  is  then  chilled  and  the  solid  waxes  and  paraffins  are 
separated  by  filtering.  The  liquid  remainder  is  then  dis- 
tilled fractionally  into  fuel  oils  and  light  and  heavy  lubrica- 
ting oils.  All  these  products  from  petroleum  and  many 
others  not  mentioned  are  composed  of  mixtures  of  hydro- 
carbon compounds  having  formulas  varying  from  C5H12  con- 

233 


234  CHEMISTRY  OF  FARM  PRACTICE 

tained  in  petroleum-ether  to  C28H56  contained  in  paraffin. 
Within  recent  years,  petroleum  in  its  unrefined  con- 
dition has  come  into  use  as  a  fuel  for  steamships  and 
for  manufacturing  purposes,  competing  successfully  with 
coal. 

183.  Kerosene.  This  is  the  most  commonly  used  source 
of  illumination  in  rural  districts.  Its  use  as  a  means  of 
temporary  or  quick  heating  is  both  economical  and  conve- 
nient. Kerosene  is  a  mixture  of  seven  hydrocarbons  ranging 
from  C10H22  to  C16H34  with  specific  gravity  varying  accord- 
ing to  the  grade  of  the  oil,  from  0.795  to  0.810.  In  the 
trade  kerosene  oil  is  classed  according  to  color  and  to  the 
temperature  at  which  the  oil  gives  off  enough  inflammable 
vapor  to  produce  a  momentary  flash  when  a  flame  is  applied. 
The  grades  of  color  are  "  Standard  White  "  (pale  yellow), 
"  Prime  White  "  (straws)  and  "  Water  White  "  (colorless). 
The  flash  tests  required  in  different  states  of  the  United 
States  vary  from  100°  F.  to  120°  F.  Water  White  oil  with 
flash-point  of  150°  F.  is  known  as  Head  Light  Oil.  Low 
flash-points  in  kerosenes  indicate  the  presence  of  benzines 
or  naphthas  whose  inflammability  makes  the  oil  dangerous 
for  use  in  lamps. 

184.  Gasoline.  This  is  formed  by  the  distillates  of  pe- 
troleum that  pass  off  at  lower  temperatures  than  that 
required  for  kerosene.  These  are  different  grades  of  gaso- 
lines, but  those  most  used  in  automobile  engines  have  dis- 
tilling temperatures  varying  between  70  and  90°  C.  cor- 
responding to  hydrocarbons  with  the  formulas  CgHu  and 
C7H10.  The  volatility  of  gasoline  enables  it  easily  to  be 
converted  into  vapor  which  when  it  is  mixed  with  air  be- 
comes highly  explosive  and  therefore  suitable  for  the  internal 
combustion  demanded  by  engines  of  the  automobile  and 
steam-launch  type. 

185.  Acetylene.  When  petroleum  oil  is  "  cracked " 
by  dropping  iii)on  plates  heated  to  a  high  temperature, 
among  the  decomposition  products  is  Acetylene   (C2H2). 


MATERIALS  PRODUCING  HEAT  AND  LIGHT        235 

It  can  be  more  easily  produced  by  dropping  water  upon 
calcium  carbide  (CaC2).  The  carbide  may  be  produced 
by  heating  to  a  high  temperature  coke  (C)  and  quicklime 
(CaO).     This  reaction  is  represented  as  follows: 

3C     +     CaO     =     CaC2     +     CO. 

Carbon  Quicklime  Calcium  Carbon 

carbide  monoxide 

Water  reacting  with  calcium  carbide  reacts  as  follows: 
CaC2     +     2H2O     =     Ca(0H)2     +     C2H2. 

Calcium  Water  Calcium  Acetylene 

carbide  hydroxide 

Acetylene  burns  with  an  extremely  hot  flame  which  in  an 
ordinary  burner  of  a  fish  tail  pattern  is  smoky.  A  special 
burner  devised  so  that  two  fine  streams  of  acetylene  mixed 
with  air  impinge  one  on  the  other  will  produce  a  very  small, 
brilliant  flame  which,  when  analyzed,  is  found  to  resemble 
in  quality  sunlight  much  more  nearly  than  any  other  illumi- 
nant.  The  equation  represented  by  the  chemical  action  in 
the  flame  is, 

C2H2     +     50     =     2CO2     +     H2O. 

Acetylene  Oxygen  Carbon  Steam 

dioxide 

The  range  of  the  mixture  of  acetylene  and  air  which  will 
explode  is  much  greater  than  that  of  other  illuminating  gases 
and  the  violence  of  the  explosion  is  far  greater  than  in  the 
case  of  other  illuminants,  therefore  mixtures  of  acetyl- 
ene and  air  are  very  dangerous.  Nevertheless  acetylene 
illumination  is  very  efl&cient.  Prest-0-Lite,  generally  used 
in  automobile  lights,  is  acetylene  dissolved  in  acetone 
(CH3)2CO. 

Acetylene  decomposes,  when  heated,  with  the  liberation 
of  a  large  amount  of  heat.  When  this  heat  of  decomposition 
is  added  to  that  produced  when  acetylene  is  burned  in  a 


236 


CHEMISTRY  OF  FARM  PRACTICE 


Fig.  76.— Fire  Extinguisher.  (Figs.  76 
and  77,  by  permission  of  Mr.  James 
C.  Goddard,  Philadelphia.) 


stream  of  oxygen,  the 
temperature  obtained  is 
remarkably  high.  Such 
a  flame  will  eat  its  way 
through  a  six-inch  steel 
shaft  in  less  than  one 
minute.  The  steel  frames 
of  modern  buildings  may 
be  rapidly  taken  apart 
by  this  flame. 

186.  Fire  Extinguish- 
ers. Fire  extinguishers 
are  effective  means  of 
extinguishing  a  fire  be- 
fore it  gains  headway. 
The  presence  of  such  a 
contrivance  may  prevent 
a  disastrous  conflagration 
and  will  surely  pay  for 
itself  in  the  peace  of 
mind  of  the  farmer  and 
his  family.  A  convenient 
form  shown  in  Fig.  76 
consists  of  a  heavy  metal 
cylindrical  container 
made  to  withstand  a 
pressure  of  350  pounds 
per  square  inch.  The 
charge  consists  of  a  sat- 
urated water  solution  of 
1^  pounds  of  sodium  bi- 
carbonate (cooking  soda, 
NaCHOa),  with  which 
the  cylinder  is  filled  to 
the  mark  and  4  fluid 
ounces  of  sulphuric  acid 


MATERIALS  PRODUCING  HEAT  AND  LIGHT        237 

in  a  glass  bottle  which  is  held  in  place  by  a  metallic 
device  which  permits  the  acid  to  flow  out  when  the  ex- 
tinguisher   is    overturned.      The    arrangement    of    these 


Fig.  77. — Working  parts  of  Fire  Extinguisher. 

1.  Position  of  acid  bottle  and  decomposing  cup  C  when  the  Underwriters 
Extinguisher  is  not  in  action.  A,  cage  for  acid  bottle.  B,  movable  support  for 
opening  cage.  C,  acid  decomposing  cup  acting  as  bottle  closure.  D,  upper  pro- 
jection or  guide  stem,  operating  in  socket  F.  E,  lower  projection  or  guide  stem, 
operating  in  the  neck  of  the  acid  bottle.  F,  socket  for  upper  guide  stem  D. 
G,  sulphuric  acid,  correct  charge  bottle  half-full.  (The  two  guide  stems  D  and 
E  center  and  hold  the  decomposing  cup  C  in  its  true  position  at  the  mouth  of 
the  acid  bottle,  either  while  the  extinguisher  is  at  rest  or  in  action,  or  in  starting 
and  stopping  it.) 

2.  Position  of  acid  bottle  and  decomposing  cup  C,  when  the  extinguisher 
is  in  action.  H,  decomposing  cup  C  filled  with  acid,  showing  point  where  the 
chemicals  come  together,  when  the  extinguisher  is  inverted.  (It  is  at  this  point 
that  the  soda  solution  attacks  and  eats  the  acid  out  of  the  decomposing  cup,  and  as 
decomposition  takes  place,  a  fresh  supply  of  acid  is  fed  from  the  bottle  into  the 
cup  as  fast  as  needed — -but  no  faster — insuring  uniform  chemical  action.) 

3.  Shows  the  depth  and  interior  of  the  porcelain  acid  decomposing  cup  C. 


materials  inside  the  container  is  shown  In  Fig.  77.  The 
reaction  between  the  sulphuric  acid  and  bicarbonate  of 
soda  rapidly  generates  carbon  dioxide,  which  furnishes 
pressure,  causing  a  mixture  of  the  solution  and  gas  to  be 


238  CHEMISTRY  OF  FARM  PRACTICE 

thrown  with  great  force  on  the  fire.  The  chemical  action 
of  the  bicarbonate  and  acid  is  as  follows : 

2NaHC03 + H2SO4  =  2CO2 + 2H2O + Na2S04. 

To  operate  the  extinguisher  it  is  turned  upside  down  and  the 
contents  played  on  the  fire  by  means  of  the  hose  attached 
at  the  top  of  the  cylinder  when  in  operation. 


CHAPTER  XXIII 
CONCRETE 

187.  Use.  Concrete  is  a  mixture  of  cement,  sand, 
crushed  rock  or  gravel  and  water.  It  is  a  most  excellent 
material  for  sidewalks,  fence  posts,  foundations,  floors  and 
walls  of  buildings,  beds  or  piers  for  machines  and  for  struc- 
tures under  water.  It  is  manufactured  in  enormous  quan- 
tities and  its  use  for  these  and  many  other  purposes  is  rapidly 
increasing.  A  hundred  millions  of  barrels  are  produced  in 
the  United  States  annually.  The  rapid  decrease  of  timber 
supply  has  made  an  urgent  demand  for  a  new  building 
material  which  is  amply  met  by  the  use  of  concrete.  On 
account  of  its  economy,  durability  and  safety  from  fire  loss 
and  ease  of  manipulation  it  is  superior  to  lumber,  brick  or 
building  stone  for  construction  purposes.  The  farmer  with 
little  assistance  and  at  convenient  times  can  use  successfully 
this  most  excellent  material. 

188.  Cement  Manufacture.  Cement  is  a  powdered, 
calcined  intimate  mixture  which,  before  heating,  contained 
in  definite  proportion  limestone  or  marl  or  chalk  (CaCOs), 
clay  (HAlSi04),  and  sand  (Si02).  In  the  manufacture  of 
Portland  cement  these  materials  are  mixed  in  the  proper 
proportions  as  shown  by  chemical  analysis,  pulverized  so 
that  it  will  pass  through  a  sieve  with  100  meshes  to  the  inch, 
burned  in  inclined  rotary  steel  cylinders  from  60  to  150  feet 
long  lined  with  firebrick.  In  these  furnaces  the  final 
temperature  rises  to  1400°  C.-1600°  C.  To  the  resulting 
clinker  is  added  a  small  amount  of  gypsum,  which  seems  to 
affect  the  time  required  for  the  setting  of  the  cement,  and 
the  material  finally  is  ground  to  a  very  fine  powder.  Natural 
cement  made  from  rock  which  has  the  correct  proportions 

239 


240  CHEMISTRY  OF  FARM  PRACTICE 

of  lime,  clay  and  sand  and  manufactured  by  heating  moder- 
ately and  grinding  was  formerly  made  in  large  quantities 
in  this  country.  Owing  to  the  cheapness  with  which  Port- 
land cement  may  be  manufactured,  with  its  properties 
governed  by  correct  admixture,  the  natural  cement  is  being 
replaced  by  the  Portland  cement.  Portland  cement  when 
properly  made  is  guaranteed  to  meet  the  standard  fixed  by 
the  American  Society  for  Testing  Materials. 

189.  Setting  of  Cement.  Cement  after  the  sintering 
process  of  the  furnace  seems  to  be  a  mixture  of  calcium 
silicate  (CaSiOa)  and  calcium  aluminate  (Ca3(A103)2).  The 
latter  seems  to  be  the  active  agent  causing  the  setting  of 
the  cement  when  it  is  mixed  with  water.  This  hydrolysis 
may  be  expressed  as  follows: 

Ca3(A103)2+6H20  =  2Al(OH)3+3Ca(OH)2. 

The  calcium  hydroxide,  crystallizing,  binds  the  particles  of 
calcium  silicate  together,  while  the  aluminium  hydroxide  fills 
the  interstices  and  makes  the  mass  compact  and  impervious. 
When  water  is  added  to  cement,  it  becomes  a  soft,  sticky 
paste  and  it  will  remain  in  this  condition  for  about  thirty 
minutes,  when  it  begins  to  harden  or  set.  To  disturb  the 
concrete  after  the  setting  is  begun  means  a  loss  in  the  strength 
of  the  concrete.  For  this  reason  the  concrete  should  be 
placed  in  position  in  less  than  thirty  minutes  after  the  cement 
is  first  wet.  There  are  several  precautions  to  be  observed. 
A  new  cement  should  neither  be  exposed  to  the  hot  sun  for 
any  considerable  length  of  time  nor  to  freezing  temperature. 
No  material  should  be  placed  on  the  freshly  made  cement 
that  will  affect  its  color.  The  cement  must  be  kept  dry, 
before  its  use,  because  it  readily  absorbs  moisture  from  the 
atmosphere  when  stored  in  damp  places;  this  causes  it 
to  become  lumpy  and  consequently  worthless  due  to  the 
setting  of  the  cement.  Lumps  may  sometimes  be  caused 
by   pressure;    these   may   often  be    broken   up   and   the 


CONCRETE  241 

cement  be  as  good  as  any,  hence  care  should  be  taken  to 
determine  the  cause  of  the  lumping  before  discarding  the 
cement. 

190.  Sknd.  Sand  constitutes  a  large  part  of  concrete. 
It  is  extremely  important  to  secure  the  proper  kind  of  sand, 
which  should  be  coarse,  clean,  hard,  and  free  from  other 
materials.  The  screening  of  the  sand  should  be  done  at 
the  source  of  supply.  This  is  accomplished  by  screening 
what  passes  a  j-inch  sieve  against  a  sieve  containing  forty 
meshes  to  the  linear  inch  and  set  at  an  angle  of  45°,  using 
the  portion  retained  by  the  sieve. 

The  following  test  will  show  the  proportions  of  sand,  clay 
and  loam  in  the  source  of  supply  of  sand:  Fill  a  pint  pre- 
serving jar  to  the  height  of  4  inches  with  the  sand  and 
add  water  to  within  1  inch  of  the  top.  The  lid  is  then 
fastened  and  the  jar  is  shaken  for  ten  minutes,  after  which 
the  contents  of  the  jar  are  allowed  to  settle.  The  sand  settles 
to  the  bottom  and  the  clay  and  other  material  gather  at 
the  top.  If  more  than  one-half  of  clay  and  loam  is  present, 
the  sand  should  be  rejected.  If  other  sand  is  not  con- 
venient, the  sand  in  question  may  be  washed.  When 
washing  is  required,  a  simple  way  is  to  build  a  board  plat- 
form 10  to  15  feet  long  with  a  12-inch  fall.  On  the  sides 
and  lower  end,  2  by  8-inch  pieces  should  be  nailed  to  hold 
the  sand.  The  sand  is  spread  on  this  platform  to  a  depth 
of  3  or  4  inches  and  is  washed  by  means  of  a  hose,  the  water 
being  applied  at  the  elevated  end  of  the  platform  and  run 
through  the  sand  and  over  the  lower  end.  The  impuri- 
ties in  the  sand  should  not  amount  to  more  than  10  per 
cent  of  the  whole. 

191.  Gravel.  The  gravel  or  crushed  stone  which  con- 
stitutes a  large  part  of  the  concrete  should  vary  from  that 
retained  on  a  j-inch  screen  to  those  that  pass  a  1^-inch 
ring.  This  material  should  be  as  free  as  possible  from 
dirt  and,  if  necessary,  may  be  washed  in  the  way  suggested 
for  sand. 


242 


CHEMISTRY  OF  FARM  PRACTICE 


192.  Quantity  of  Materials  for  a  Given  Mixture.  Con- 
crete is  a  manufactured  stone  and  the  object  is  to  fill  the 
interstices  between  the  gravel  with  sand  and  those  between 
the  sand  particles  with  cement,  hence  the  volume  of  con- 
crete is  just  about  represented  by  the  volume  of  crushed 
stone  or  gravel.     A  mixture  consisting  of  one  part  by  vol- 

fmmm 


-12  — 


Concrete 


Cement  Sand  Stone 

Fig.  78. — Required  quantities  of  cement,  sand,  and  stone  or  gravel 
for  a  1  :  2  :  4  concrete  mixture  and  the  resulting  quantity  of  con- 
crete.    (Bulletin  461,  U.  S.  Dept.  Agr.) 

ume  of  cement,  and  two  parts  of  sand  and  four  parts  of  stone 
or  gravel,  is  often  used.  Table  XXIV  gives  the  quantities 
of  the  various  materials  for  cement  or  concrete  mixtures; 
the  relative  values  are  shown  in  Fig.  78. 

TABLE  XXIV.— QUANTITIES  OF  MATERIALS  AND  THE 
RESULTING  AMOUNT  OF  CONCRETE  FOR  A  TWO- 
BAG  BATCH. 

(Farmer's  Bulletin  461,  U.  S.  Dept.  Agr.) 


Proportions 

Ma 

Sizes  op  Measuring    Boxes 

BY 

Parts. 

(Inside  Measurements). 

^ 

e'3' 

^— 

o 

o 

3  o 

Kinds  of 
Concrete 
Mixture. 

> 

2 

a 

03 

<u 
o 

s 

X> 

3 
o 

Sand. 

Stone  or 
Gravel. 

11 

o  h 

fl 

a 

X: 

a 

-a 

o 

a 

0 

6 

a 

a 

6 

1  :2  :4.. 

1 

2 

4 

2 

3} 

7i 

8J 

2   feet   by   2 
feet  by  Hi 
inches. 

2    feet    by   4 
feet  by   11 J 
inches. 

10 

1  :2i  :5. 

1 

2i 

5 

2 

4i 

9i 

10 

2  feet  by  2  feet 
6  inches  by 

2  feet  6  inches 
by  4  feet  by 

12J 

11 J    inches. 

Hi  inches. 

CONCRETE 


243 


If  the  sand  is  very  fine,  the  pore  space  will  be  increased, 
and  therefore  a  little  more  cement  will  be  required.  The 
materials  should  be  mixed  until  they  assume  a  uniform 
color.  If  after  thorough  mixing  the  batch  does  not  work 
well,  the  sand  and  cement  does  not  fill  the  spaces  between 


Fig.  79. — Concrete  board  and  tools  for  making  concrete.     (Farmers' 
Bulletin  461,  U.  S.  Dept.  Agr.) 

the  stones,  the  proportion  of  stone  should  be  reduced  in 
succeeding  batches. 


TABLE   XXV.— QUANTITIES   OF   MATERIALS   IN    1    CUBIC 
FOOT  OF  CONCRETE 


Mixture  of  Concrete. 

Cement 
(by  Barrels). 

Sand  (by 
Cubic 
Yards). 

Stone  or 

Gravel  (by 

Cubic 

Yards). 

1  :2 : 4 

1  :  2i  :  5           

0.058 
.048 

0.0163 
.0176 

0.0326 
.0352 

244 


CHEMISTRY  OF  FARM  PRACTICE 


Table  XXV  gives  the  quantities  of  each  material  required 
in  1  cubic  foot  of  concrete.  With  this  data  it  is  easy  to 
calculate  the  amount  of  material  for  any  given  structure. 
A  sack  of  cement  contains  1  cubic  foot  of  cement  and  four 
sacks  constitute  a  barrel. 


Fig.   80. — Concrete  watering  trough.     (From    Howe  s   ""  Agricultural 

Drafting.") 


Example.*  Let  us  suppose  that  the  work  consists  of  a 
concrete  silo  requiring  in  all  935  cubic  feet  of  concrete,  of 
which  750  cubic  feet  are  to  be  1  :  2  :  4  concrete,  and  185 
cubic  feet  are  to  be  1  :  2^  :  5  concrete.  Enough  sand 
and  cement  are  also  needed  to   "  paint  "   the  silo  inside 

*  From  U.  S.  Dept.  of  Agr.  Bulletin,  461. 


CONCRETE  245 

and  outside,  amounting  in  all  to  400  square  yards  of  surface, 
with  a  1  :  1  mixture  of  sand  and  cement.  One  cubic  foot 
of  1  :  1  mortar  paints  about  15  square  yards  of  surface  and 
requires  0.1856  barrel  of  cement  and  0.0263  cubic  yard 
of  sand.     The  problem  thus  works  out  as  follows: 

Cement:  Barrels. 

For  the  750  cubic  feet  of  1  :  2  :  4  concrete  (750  X 0.058) ...  43 . 5 
For  the  185  cubic  feet  of  1  :  2J  :  5  concrete  (185X0.048) .  .  8.9 
For  painting  (400^-15X0.1856) 4.9 

Total  amount  of  cement 57 . 3 


Sand:  Cubic  Yds. 

For  750  cubic  feet  of  1  :  2  :  4  concrete  (750X0.0163) 12.23 

For  185  cubic  feet  of  1  :  2|  :  5  concrete  (185X0.0176) 3.26 

For  painting  (400-^15X0.0263) 70 

Total  amount  of  sand 16.19 

Stone  or  gravel: 

For  750  cubic  feet  of  1  :  2  :  4  concrete  (750X0.0326) 24,5 

For  185  cubic  feet  of  1  :  2i  :  5  concrete  (185X0.0352) '   0.5 

Total  amount  of  stone  or  gravel 31.0 

V 

Thus  the  necessary  quantities  of  materials  are  about 
57|  barrels  of  Portland  cement,  about  16j  cubic  yards  of 
sand,  and  31  cubic  yards  of  stone  or  gravel. 

193.  Mixing  Concrete.  In  mixing  concrete  the  sand  is 
first  spread  over  the  mixing  floor  in  a  layer  3  or  4  inches  in 
depth.  The  cement  is  then  spread  evenly  over  the  sand. 
These  materials  are  then  mixed  thoroughly  with  a  shovel, 
the  mixture  is  spread  over  the  floor  and  the  gravel  is  added. 
About  three-fourths  of  the  water  to  be  used  is  then  thrown 
as  evenly  as  possible  over  the  gravel  layer  and  the  materials 
are  again  thoroughly  mixed  with  the  shovel.  Water  should 
be  added  to  the  dry  spots  as  the  mixing  proceeds,  until 
the  full  amount  has  been  used.  After  thoroughly  mixing, 
the  concrete  is  shoveled  into  a  compact  pile. 


246 


CHEMISTRY  OF  FARM  PRACTICE 


194.  Placing  the  Concrete.  Concrete  should  be  placed 
immediately  after  mixing.  Wooden  forms  to  give  the  shape 
of  the  structure  to  be  built,  Fig.  81,  are  required  and  should 
be  ready  before  the  concrete  is  mixed.  In  placing  the 
concrete,  the  shovel  should  be  run  down  along  the  face  of 
the  form  to  press  the  gravel  back  and  allow  the  cement  to 


Fig.  81. — Forms  for  concrete  watering  trough.     (From  Howe's  "Agri- 
cultural Drafting.") 

flow  against  the  form,  thus  producing  a  smooth  and  finished 
surface  when  the  form  is  removed. 

New  concrete  should  not  l)c  exposed  to  the  sun  until 
after  it  has  hardened  for  five  or  six  days.  The  forms  should 
be  left  in  place  till  the  concrete  has  "  set  "  thoroughly. 
To  permit  removal  of  the  forms,  the  surface  should  be  wet 
daily. 


INDEX 


PAGE 

Acetylene 234 

Acids,  characteristic  properties  of 24 

Air  in  soils 63 

Alunite 143 

Animal  nutrition 174 

digestible  nutrients 176 

metabolism 176 

foods,  classes  of 174 

Anhydrides 27 

Atoms 3 

Babcock  test  for  butter  fat 204 

Bacteria,  nitrogen  fixing 64 

nitrifying 64 

Bases,  properties 25 

Boracic  acid,  milk  preservative 202 

detection  of 204 

Butter 209 

composition  of 210 

process 210 

Calcimine 230 

Calcium 42 

phosphate 23 

Carbohydrates 174 

Carbon 35 

Carbonates 66 

Carbon  dioxide,  effect  on  decay 65 

Cheese 210 

Combustion 8 

spontaneous 11 

Combustibles 8 

Compounds 13 

classes  of 24 

nomenclature 29 

247 


248  INDEX 

PA.OE 

Concrete 239 

cement  manufacture 239 

gravel 241 

mixing 245 

placing 246 

sand 241 

setting  of 240 

Crops,  proper  sequence  of 86 

residues,  composition  of 85 

Digestibility,  coefficient  of 194 

Disinfectants 219 

lime 219 

chlorinate 219 

bichloride  of  mercury 225 

carbolic  acid 222 

crude 222 

cresol 223 

formaldehyde 220 

sulphur 222 

Dissociation 28 

Elements 1 

groups  of 24 

Equations 19 

Fats 175 

Feeding  standard,  Wolff-Lehman 177 

Feeds,  composition 192 

concentrates 184 

barley 184 

blood  meal 188 

corn 184 

cottonseed  meal 186 

dried  brewers'  grain 185 

dried  fish 188 

linseed  meal 187 

meat  scraps 188 

oats 184 

peanuts 189 

rice,  polish 186 

meal 186 

rye 185 

soybean  meal 189 

wheat,  bran 185 

middlings 185 


INDEX  249 


PAGE 


Fertilizers,  incompatibilities,  diagram  showing 167 

mixing  of 162 

advantages  of  home-mixing 162 

may  be  thoroughly  mixed  on  farm 163 

educational  value  of  home-mixing 165 

calculations  of  formulas 165 

Fire  extinguishers 236 

Formalin,  as  a  milk  preservative 201 

detection  of 203 

Formulas 16 

Food  stuffs,  average  digestibility 88 

Fungi,  injurious 212 

Fungicides 216 

Bordeaux  mixture 216 

lime-sulphur 216 

self  boiled 217 

sulphur;  finely  divided 217 

copper  sulphate 218 

ammoniacal  copper  carbonate 219 

formaldehyde  solutions 219 

Gases,  diffusion  of 67 

Gasolene 234 

Glue 231 

Hydrates 16 

Hydrogen 34 

Insects,  injurious,  classification 212 

Insecticides,  for  biting  insects 213 

Paris  green 214 

lead  arsenate 213 

green  arsenoid 215 

London  purple 215 

for  sucking  insects 215 

kerosene  emulsion 215 

soaps 215 

lime-sulphur 215 

nicotine  solutions 215 

sulphate  solutions 215 

carbon  bisulphide 216 

hydrocyanic  acid  gas 216 

Ions 28 

Iron 42 

Kerosene 234 

Land,  keeping  covered 90 


250  INDEX 

PAGE 

Land  plaster : 105, 114 

Legumes 38 

Lime,  agricultural 97 

application 101,  104 

burning  on  the  farm 99 

dangers  from  use 100 

effects  on  soils 97 

machine  for  applying 104 

plants,  improved  by 103 

plant  injured  by 103 

shipping 100 

sources  of 97 

Magnesium 42 

Manures,  uses  of 87 

effect  of  exposure  to  weathers 95 

factors  affecting 92 

horse,  properties  of 95 

liquid 92 

plant  food  content  of  solid  and  liquid 93 

rate  of  application 96 

rotted,  composition  of 93 

Materials  for  bedding,  composition  of 93 

Matter,  conservation  of 13 

Milk,  composition  of 198 

ash,  determination  of 209 

city  requirements 201 

condensed 211 

fat,  determination  of 204 

infected,  dangers  from 199 

preservatives 201 

solids,  total,  determination  of 209 

specific  gravity,  determination  of 208 

Mixtures,  mechanical 14 

Molecules 3 

Nitrification 48 

Nitrogen,  properties 37 

fixation  of  atmospheric 38 

importance  of 120 

commercial,  profitable 122 

selection  of  source  of 122 

inorganic  sources 124 

potassium  nitrate 126 

sodium  nitrate 127 


INDEX  251 

PAGE 

Nitrogen,  inorganic  sources,  calcium  nitrate 130 

ammonium  sulphate 132 

organic  sources 132 

dried  blood 132 

ground  fish 132 

tankage 132 

Peruvian  guano 133 

hoof  meal 133 

hides,  horns,  hair,  etc 133 

wool 133 

bone 134 

cottonseed  meal 134 

rapeseed  meal 134 

linseed  meal 134 

castor  pomace 134 

calcium  cyanamide 135 

Nutrition,  animal 174 

Oils,  drying 225 

Oleomargarine 210 

Osmosis 71 

Oxidation 7 

Oxygen 32 

importance  of 66 

Paints 225 

driers 226 

mixing 229 

Petroleum 233 

Phosphate,  bone 107 

Phosphoric  acid,  reverted 107 

Phosphorus 38 

presence  in  the  soil 107 

as  a  limiting  factor 108 

commercial  sources 108 

phosphate  rock 110, 118 

acid  phosphate 112 

Thomas'  phosphate 114 

bone 114 

mineral  phosphate 115 

phosphatic  guanos 116 

purchase  and  appUcation 117 

Photosynthesis 73 

Pigments,  white  lead 226 

subhmed 226 


252  INDEX 


PAGE 

Pigments,  white  Chinese 227 

Uthophone 227 

barytes 227 

green,  Brunswick 227 

chrome 227 

blue,  ultramarine 228 

Prussian 228 

red,  lead ' 228 

iron 228 

vermilion 228 

yellow,  chrome 228 

chromate,  lead 228 

ochres 228 

brown,  umbers 228 

Vandyke 228 

black,  lampblack 228 

Plant  food,  availability  of 48 

source  of 70 

forms  of 152 

measuring  requirements 152 

field  tests 158 

Plant  leaves,  functions  of 73 

leachings  from 74 

food,  gain  and  loss  of 82 

Plants,  root  systems  of 70 

Potassium 39 

Potash,  salts,  occurrence 137 

organic  sources 140 

minor  sources 140 

wood  ashes  as  source  of 140 

commercial  salts 143 

Proteins 174 

Radicals 17 

Rations 179 

growth 179 

maintenance 180 

fattening 181 

milk-cows 182 

work  animals 182 

calculations  of 194 

Salts 26 

Shellac 231 

Soil  components 59 


INDEX  253 

PAGE 

Soil  analysis 152 

methods 153 

Soils,  formation  of 76 

composition  of 79 

classification 81 

Sulphur 39 

Symbols 5,  6 

Temperatures,  kindling 9 

Valence 6, 14 

Varnishes 230 

spirit 231 

oil 231 

Water,  properties  of 44 

solvent,  action  of 46 

drinking 49 

borne  diseases 49 

spring 50 

shallow  wells 50 

deep  wells 51 

factors  influencing  attractiveness  of 52 

hardness 52 

temporary,  remedies  for 53 

permanent,  is  removed 54 

filtered 55 

boiled 56 

distilled 56 

boiler 56 

treatment 58 

requirements  of  plants 59 

soil 60 

capillary 60 

gravitational 60 

Weights,  atomic 3,  6 

molecular 5 

Whitewash,  Government 229 

factory 229 

waterproof 230 

special  ingredients  for 230 


THE  WILEY  TECHNICAL  SERIES 

,       .  EDITED    BY 

JOSEPH   M.   JAMESON 


A  series  of  carefully  adapted  texts  for  use  in  technical, 
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MECHANICS  AND  MATHEMATICS 

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PRACTICAL    SHOP    MECHANICS    AND    MATHEMATICS. 

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AGRICULTURE  AND  HORTICULTURE 

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lABORATORY    MANUAL   IN   GENERAL   MICROBIOLOGY. 

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THE    LOOSE   LEAF  LABORATORY  MANUAL 


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THE  LOOSE  LEAF  LABORATORY  MA^VAL-Cont. 


MECHANICS  AND  HEAT 

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THE  LOOSE  LEAF  LABORATORY  MANUAL-Con<. 


AGRICULTURE  AND  HORTICULTURE 

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This  book  is  DUE  on  the  last  date  stamped  below 

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JUL  tl  IW 


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